ARC Raiders players are running into a family of errors that talk about “illegal mutations” and “illegal backend mutations.” The wording sounds like an anticheat trigger or a ban, but in most cases it points to something much simpler: the game client and the backend no longer agree about the state of your inventory or account.
These errors show up in a few slightly different forms:
| Error text / code | Typical trigger | What the game does |
|---|---|---|
| “An illegal mutation was rejected by the backend. The inventory has been rolled back to its previous state. We have to redirect you back to the Main Hub.” | Server-side rollback during or after a raid, often during wider outages | Kicks you to Main Hub, items revert to last known good state |
| ARBG0000 – “Illegal Backend mutation” | Account save or quest state desync; UI popups can spam the screen | Prevents interacting with menus; in severe cases you can’t play on that account |
| ARON1400 – “An illegal mutation was rejected by the backend…” | Recycling or dismantling ARC parts or other items | Specific action fails; inventory may roll back or refuse to change |
Why ARC Raiders shows “illegal mutation” and rollback messages
ARC Raiders runs most of its important logic on Embark’s servers, not on your local machine. Every time you craft an item, sell loot, dismantle a part, or finish a raid, the game sends a “mutation” to the backend describing how your inventory and account state should change.
The “illegal mutation” wording appears when the backend rejects that proposed change. Common reasons include:
- The server believes you don’t own the items or currency you’re trying to spend or sell.
- The stack sizes or counts on the client don’t match what the backend has stored.
- Two actions hit the same item or slot at nearly the same time (for example, repeated crafting clicks during lag).
- The backend is under heavy load or in the middle of an outage, so it refuses or rolls back state updates.
When that happens, the game falls back to the last state the backend is confident about. That is why players see messages about the inventory being “rolled back to its previous state” and then get sent back to the Main Hub.
Link between illegal mutation errors and server outages
The errors become much more visible when ARC Raiders’ servers are struggling. During large outages affecting tens of thousands of players, connection errors like “Online connection error” show up alongside the illegal mutation rollback message. In those windows, the backend is dropping connections, timing out, and sometimes resetting inventory changes that were in-flight.
Players report:
- Finishing a raid and immediately getting an illegal mutation message before reaching the Hub.
- Seeing inventory changes (like repairs or crafts) apparently succeed, then revert after a pop-up.
- Being unable to log back in at all, right after an illegal mutation error during matchmaking or when dumping backpack contents into the stash.
During these larger incidents, illegal mutations are more symptom than root cause. The real problem is that the servers can’t reliably accept or verify state changes, so they reject anything that looks uncertain and roll it back.
ARBG0000 “Illegal Backend mutation” as an account sync bug
ARBG0000 is a specific code that points to a deeper account-level sync problem rather than a single failed action. Players hit by ARBG0000 describe a loop where the error pop-up continuously respawns over the UI, making it impossible to click menus or start runs.
Characteristics of ARBG0000:
- Starts after a bad sync between your account and the backend (often around a quest or progression step).
- Reinstalling the game or clearing local files does not help, because the corrupted or mismatched state lives on the server.
- The problem can be tied to your profile itself: a fresh ARC Raiders account on the same machine works normally.
In this scenario, the backend is convinced that something about your account state is invalid, so every attempt by the client to apply further changes is rejected with the same error. Until the backend state is cleaned up or bypassed, the client stays stuck in that loop.
What players are doing that triggers illegal mutation errors
The messages often show up around very ordinary actions:
| Player action | Observed effect |
|---|---|
| Crafting multiple items (e.g., shield rechargers) during lag | Client briefly shows new items, then an illegal mutation error appears and some of the craft attempts are rolled back. |
| Repairing a weapon | Error message flashes, but the gun may still end up repaired; the backend likely accepted the mutation but flagged a minor discrepancy. |
| Selling or recycling loot, including small items like rubber pads or an “air freshener” | Illegal mutation or ARON1400 error when the sale/recycle is sent; inventory or currency may revert. |
| Dumping backpack contents into stash after a raid | On consoles and PC, players report an illegal mutation message followed by being unable to reconnect. |
In normal conditions, these actions are safe. When servers are unstable or your account state is slightly out of sync, they can be enough to surface the underlying mismatch.
Is “illegal mutation” a cheating or anticheat warning?
Some comments interpret the wording as proof that someone edited their save or tripped an anticheat. The terminology does come from the same basic idea — a “mutation” that fails validation — but in practice, players see these errors while:
- Running stock clients with no modifications.
- Playing on consoles where local file editing isn’t practical.
- Performing basic inventory management or completing standard quests.
When thousands of players hit the message during a server outage, it clearly isn’t limited to cheaters. The backend is designed to reject any state change that doesn’t cleanly line up with its records, which includes desyncs from lag, rollback during crashes, or partially applied quest steps. The system does not differentiate between a malicious and a broken client in the wording it shows you.
Actual enforcement actions (like bans) are handled separately; the “illegal mutation” copy on its own does not automatically mean punitive action has been taken.
Player workarounds for ARBG0000 and other illegal mutation loops
There is no guaranteed, client-side fix for ARBG0000 or for inventory corruption on the server, but players have found a few ways to get unstuck or at least keep playing.
Force a failed sync, then reconnect
One workaround targets the underlying desync directly:
- Launch ARC Raiders and load into the game with your affected account.
- Before the usual crash or spam of ARBG0000 pop-ups, disconnect your internet (unplug Ethernet or disable Wi-Fi).
- Wait for the game to recognize the lost connection and fail the current sync.
- Reconnect your internet and let the client attempt a fresh sync when it retries.
When this works, it forces the backend to throw away the broken pending state and resync from a clean snapshot, clearing the ARBG0000 loop.
Clear up messy stacks and finish stuck quests
On accounts where the game remains usable but illegal mutation pop-ups are frequent, some players report better behavior after:
- Using an autoclicker or very fast manual clicking to push through UI pop-ups long enough to complete a bugged quest.
- Cleaning inventory stacks so that as many item types as possible are in full, neat stacks (for example, ammo stacked to its expected maximum, leaving only a single partial stack).
The idea is simple: the fewer edge-case stack sizes and half-updated items your account has, the easier it is for the backend to reconcile a consistent state. In some cases, once the problematic quest or item stack is resolved, the illegal mutation messages become rare or disappear.
Create a new ARC Raiders account when the profile is bricked
When ARBG0000 hits so hard that you can’t interact with any menu, the only fully reliable way players have continued playing has been to create a new profile:
- Create a fresh Embark account if you’re on PC, or log in with a different platform account on console.
- Start ARC Raiders with that new identity.
This completely bypasses the corrupted save state, at the cost of all progression, items, and unlocks on the original account. It is a last resort, but it confirms that the bug lives in the backend profile, not on your hardware.
What does not help with illegal backend mutation errors
Because the problem is server-side, several common troubleshooting steps are largely ineffective:
- Reinstalling the game: Does not change the backend’s view of your account or inventory.
- Verifying game files: Useful for crashes or missing assets, but it does not touch your server save.
- Power cycling your console or PC: May clear local caches and transient network issues, but a persistent ARBG0000 or rollback loop will immediately return if the backend state remains broken.
These steps are harmless to try once, especially if you suspect a local connectivity problem, but they should not be expected to repair illegal mutation issues on their own.
How much progress can be lost when inventory is rolled back
When the backend rolls your inventory back, it resets to the last point where it recorded a coherent state. That can mean:
- Losing loot from a raid that ended right as the servers went unstable.
- Undoing several trader runs if those transactions never fully committed.
- Reverting item repairs, crafts, or dismantles that were in-flight during an outage.
In some cases, players see a rollback message but, after inspecting their stash, find that little or nothing meaningful changed. In others, hours of work since the prior session checkpoint can vanish. The variability depends entirely on when the backend last wrote a solid snapshot for your profile and how much action happened after that point.
What players can realistically do while waiting for server-side fixes
Since the root causes are within Embark’s backend logic and infrastructure, the long-term solution has to come from server patches and better handling of desyncs. In the meantime, the most practical steps for players are:
- Avoid heavy inventory management or high-value trades during obvious server instability or connection errors.
- If you see repeated illegal mutation messages, but can still move around menus, clean up odd stacks, and finish any quests that seem to be firing the pop-ups.
- Use the disconnect–reconnect sync reset trick once if you’re stuck in an ARBG0000 loop, before giving up on the profile.
- When completely bricked, decide whether creating a new account is worth the lost progress.
The “illegal mutation” language makes these errors sound more dramatic than they are. In practice, they are the backend’s way of saying, “this change doesn’t match what I know about you, so I’m rewinding to the last safe point.” Until the server-side validation and rollback logic becomes more forgiving, players will keep bumping into that message whenever ARC Raiders’ live service layer stumbles.
