I've been in the water with 3 uncontrolled ascends nearby I involved myself with. A bonus story of my own too.
1. Diving with my friend. His wing inflator stuck. Couldn't dump while trying to disconnect it in 3mm gloves. I couldn't/didn't risk catching him by the time I realized his situation I would have needed a wild ascent rate and he has probably 40lbs positive buoyancy. I could not have kept him down. I let him go and he survived. It haunted me.
2. I was shallow and watched a group of divers below me. Noticed one was having trouble at the back of the group. I stayed above him (60ft maybe) about 10 minutes later he fully inflated his bcd. Saw him coming, deflated my bcd (overweighted) and finned down to catch him by the tank and dump valve. My thrust slowed us to a safer ascent rate, went around to face him and ascended. He had inhaled water and panicked. Surface he was glad for the company.
3. Again, saw a group of divers with one having trouble, nearby, at 50ft. One guy looked like he confused his deflate and inflate. Started going up. I caught him by a fin... But I was neutrally buoyant with no bcd... He started pulling me to the surface and I tried to "climb" him to reach his inflator. I got my mask dislodged and I returned to holding his waist and splaying out my fins to slow us. Probably should have let go. Surface we both were fine.
4. I've corked myself with a stuck bcd inflator. (Lp131 doubles and a deco bottle, drysuit and 40° water thermals, 5mm wet gloves) Missed finding my dump valve and by the second try I was already over inflated and going up. Drysuit wasn't venting fast enough either. Up I went. No harm (early in the dive with no deco obligation yet) but it gets F.U.B.A.R. faster than expected if the initial response isn't properly executed. I had considered myself proficient and in drills it is easy to disconnect the lp inflator and dump....
Not sure if this has any relevancy but that's what I've seen. (Plus watched a ton of corking new students in Caribbean locations.)
Cameron