The plate dropping probably set off a startle effect.
If you jumped or tensed up it can make your muscles tighten and it will affect your breathing until you get relaxed again.
The fight or flight response, it triggers an adrenaline release too..
You can read online about that and it may helps you understand why these things are setting you off.

I suggest trying to be nearly symptom free for months before slowly getting back into crowds and triggering activities.