Yes. Not that long ago I was stuck in a flashback unable to move or speak. I don't know how to overcome it yet but you ain't alone in this

The trick is to stop the flashbacks and then there's no reason you'd become nonverbal. To stop the flashbacks you need a combination of medication and therapy. My medication is constantly being increased because I have MDD that is probably untreatable. Therapy has been working for me recently with my new therapist so I'm hopeful

I have dealt with this and honestly I have the same question

We get non verbal when we're really run down and mentally tired so it's the same for us with flashbacks too.. we don't know how to deal with them and we often get them when we lay in bed at night