Quick answer: Cancel all damage-over-time effects the moment an actor dies, and have each tick check the actor is still alive before applying damage.
A poisoned enemy that dies from the poison should stop ticking immediately, not keep firing and stall the victory check. If yours lingers, nothing cancels the effect on death. Here is the fix.
How to fix it
1. Guard each tick
At the top of the tick, return early if actor.currentHP <= 0 or actor.IsDead. Never apply damage to a downed unit.
2. Clear effects on death
In your death handler, stop poison/burn coroutines and clear the actor's status list so no pending tick fires next turn.
3. Decouple the victory check
Run the win/lose check after each tick resolves so a poison kill ends the battle instead of waiting on a phantom living enemy.
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.