How to Fix Save Corruption When Two Game Instances Write the Same File

Two instances saving to the same path interleave their writes and corrupt the file. A single-instance lock plus atomic writes keeps the save consistent.

How to fix it

1. Enforce single instance

Acquire a named OS mutex or create a lock file on launch. If it already exists, focus the running game instead of starting a second writer.

2. Make writes atomic

Write to a temp file and rename it over the save, so even if a second process slips through, each write is all-or-nothing rather than interleaved.

3. Clean up stale locks

On a crash the lock file may linger. Store the PID in it and ignore the lock if that process is no longer running, so players are not locked out.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.