Stuck inside possession, esc or space don't exit.

I've been playing the Heart of Gold campaign and in the last two maps of the campaign I've encountered a bug that made me unable to leave the possession of a unit. In the last map, I've been possessing the Colossus with no problem in order to destroy the inhibitors, but for some reason (I can't seem to find out what the trigger is) at some point I become unable to leave the possession and in this case my last auto-save was while in possession. When this bug happens all I can do is alt+f4 or terminate the game process, because other inputs unrelated to possession, such as quick-load or quick-save, do not seem to do anything. The possessed unit can still be used to move around/attack etc.

When I try to load this auto-save, I'm not in possession anymore, but sometimes I can't use any spells or hotkeys, though the menu will still work; and if I load this auto-save and I try to make a separate save, the game simply crashes. Unfortunately, the first time I tried saving over my previous save, and that save got corrupted and removed.

I tried to look for a crash log, but I am unable to find one. I can try to make a video of this happening, if that's helpful.

It's quite frustrating to lose so much progress in this large map just over a bug with possession which I haven't seen mentioned, and I suppose I will just avoid possession altogether to do the map now, but it was really handy.