The `ChildSpanFinished` method checks `_hasFinished` before calling `_idleTimer?.Start()`, but there's a race condition: `Finish()` could be invoked concurrently between the check and the `Start()` call. `Finish()` disposes the timer after setting `_hasFinished`, so `Start()` would then throw `ObjectDisposedException`. The similar method `ResetIdleTimeout` (line 395-403) explicitly handles this race with a try-catch, but `ChildSpanFinished` does not. This could cause runtime exceptions when a span finishes while the transaction is concurrently finishing.