Task.Delay( nextLevelDelay ) uses milliseconds, so the intended multi-second wait before loading nextscene is actually 3 ms.

OnTriggerEnter ignores the collider argument and has no guard, so any collider entering the volume starts another save and scene load.

DelayedMethod passes nextLevelDelay (3) straight into Task.Delay, which takes milliseconds, so the next scene loads after 3 ms instead of the intended seconds.

OnTriggerEnter calls LoadNextLevel without awaiting it and DelayedMethod is async void, so the delay and the scene load run detached from the trigger callback.