I was wondering what does "stay animated" checkbox do, so i created advanced door with stay animated enabled, opened and closed it couple of times, but when i tried to remove it, i failed, even in closed state it doesn't have hitbox like other doors and can't be destroyed, only oppened and closed

You can only destroy the animation using a wrench. Right click on the door with a wrench and click Destroy Animation

Yep, it works, thanks