How to Fix Unity Timeline Signal Emitter Firing Twice on a Looping Director

A signal firing twice per loop is being evaluated on both sides of the loop seam. Moving it off the boundary fixes it. Here is how.

How to fix it

1. Move the signal off the boundary

Place the Signal Emitter a few frames inside the clip rather than exactly at time zero or at the duration, so a loop wrap does not evaluate it on both the end and the restart.

2. Check the wrap mode

If the cutscene should play once, set the director's Wrap Mode to Hold or None; a Loop wrap re-enters the start each pass and re-triggers boundary signals.

3. Debounce in the receiver

Guard the SignalReceiver handler so it ignores a second call within the same loop pass (track a last-fired time or pass index), making the side effect idempotent.

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 Unity 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.