How to Fix “Multiple EventSystems in scene” in Unity

The multiple-EventSystems warning appears when additive scenes each carry their own. Two EventSystems fight over UI input, causing clicks to misbehave. Here is how to keep just one.

How to fix it

1. Remove EventSystems from additive scenes

If you load scenes additively, only one should contain an EventSystem. Delete it from the others so loading them does not add a second.

2. Destroy extras at runtime

Add a guard that checks for an existing EventSystem on Awake and destroys the duplicate, keeping the first one. This mirrors the singleton pattern and survives additive loads.

3. Put it in a persistent bootstrap scene

Place a single EventSystem in a bootstrap scene that loads once and persists, so gameplay scenes never need their own and duplicates cannot appear.

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.