Quick answer: Stamp each projectile with its owner's team, and before applying damage compare teams and the friendly-fire flag to decide whether the hit counts.
Flipping off friendly fire does nothing if the projectile never checks teams. Tagging projectiles with their owner's team and gating damage fixes it. Here is how.
How to fix it
1. Tag the projectile with a team
When spawning, set projectile.team = shooter.team so the projectile knows who fired it and which side it belongs to.
2. Gate damage by team and flag
On hit, if target.team == projectile.team and friendly fire is off, return without applying damage. Otherwise proceed normally.
3. Expose the flag in one place
Keep the friendly-fire boolean in a single autoload/settings node so the toggle the player flips is the same one every projectile reads.
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 Godot 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.
Most of the time the fix is small. Seeing the failure clearly is the part that actually costs you.