How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix a Unity ScriptableObject Event Channel With Stale Listeners

Q: What causes a Unity ScriptableObject event channel with stale listeners?

The SO event channel holds its listener list as asset state that survives Play Mode, so listeners that never unsubscribed accumulate and dead objects get invoked.

Quick answer: Subscribe in OnEnable and unsubscribe in OnDisable, and clear the channel's listener list on Play Mode exit so subscriptions never carry over between sessions.

Your SO-based event channel fires twice, or invokes an object you destroyed last session. The channel is an asset, so its listener list persists. Symmetric subscribe/unsubscribe and a reset fix it.

How to fix it

1. Subscribe and unsubscribe symmetrically

Register in OnEnable and always deregister in OnDisable; an asymmetric pair is what leaves dead listeners on the channel.

2. Clear listeners on Play Mode exit

Because the channel is an asset, reset its listener list when leaving Play Mode (via OnDisable on the SO or a play-mode hook) so the editor copy starts clean.

3. Guard against duplicates

Before adding a listener, remove it first or use a set, so a double OnEnable from re-activation cannot register the same handler twice.

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.

Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.