I have a sexual parasomnia - while this hasn’t happened in at least 15 years, I used to initiate sex while asleep. I have no memory of it, but I have groped, kissed, sucked on the fingers of people, and sexually touched people sleeping next to me.
I’ve always woken up just before sex occurred, but I’ve accidentally had sex with people before - people who I was attracted to, but maybe didn’t want to bang - because we fell asleep together.

These days I’m not nearly in as many beds as I used to be (regardless of purpose) but I’m also an incredibly light sleeper now. The slightest movement and my conscious brain takes over. (Yay for newly(ish) developed hyper vigilance and anxiety.)
With that said, I don’t sleep next to anyone anymore unless we’ve had a conversation about what could happen, and are on the same page.

To your point about discussing things: The topic of consent around something that I’m not consciously aware is of occurring can be challenging as hell to navigate, but easier than not having a chat beforehand.