Quick answer: Write user data to the user's profile locations (Saved Games, AppData, or platform-prescribed paths) and migrate old install-folder saves on first run.
Writing beside the exe worked in 2005 and produces permission failures, phantom saves, and update-wiped progress today. The fix is the standard save path plus a migration. Here it is.
How to fix it
1. Use the prescribed locations
Windows: %USERPROFILE%/Saved Games or %APPDATA%/YourGame (engines expose these — Godot's user://, Unity's persistentDataPath); never a path derived from the executable's directory.
2. Beware VirtualStore ghosts
Legacy 32-bit games writing to Program Files may 'work' via VirtualStore redirection — saves that survive but hide, breaking support instructions and cloud sync; moving to real paths ends the haunting.
3. Migrate existing players
First run of the fixed build: check the old location, copy saves to the new one, leave a marker — silent save loss on update is a review catastrophe.
4. Report save-write failures
Wrap save I/O with error capture including the path — permission failures, full disks, and sync-locked files become diagnosable reports instead of 'my progress vanished' reviews.
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.
The bug you can't reproduce isn't gone — it's just invisible until you capture it from the player's device.