...

Are you insane? Why ever would she do that? What good does it achieve? They can't do anything remotely useful but just wander around aimlessly.

Whenever you discover them, he alerts you via his usual "you found an object" responses that you found a Shrine.

Alright, I'll write steps to reproduce, if any are figured out. But on the topic, why don't you just disallow placing banners inside the Prison and the Arena?

After loading a savegame it appears they don't respawn there anymore. They were still present there after reloading tho.

It seems like a general issue. Just came across a 3x3 Torture Chamber on the level 10 that had the same corner glitch. And earlier a Slaughterpen was found with this glitch again. Do you think the Stone Bridge capture glitch I have reported before has anything to do with this? From the looks of it, some tiles visually disconnect in a similar manner, forming whole new 1x1 rooms.

If I'm right, accidentally placing one inside your Prison can make all prisoners escape/glitch outside. Check out my other report regarding the Arena and a rally banner in it.

It appears to be a scripting issue. The Huntress keeps to spawn there as I kill her with Lighting. Damn. She takes out everything I prepared for enemy assault.

Same goes to all other constructs, I guess?

I've seen a level 4 Gnarling fleeing from 3 level one Sappers... 'nuff said, I think. No, he wasn't even scratched. The sappers just finished breaching in.

What? First of all, try to reset campaign sometime, a dialog box will ask for confirmation and warn it will delete save files as well as overall progress. And it did in fact delete almost all of them but the ones mentioned in the OP.