The new build mode has a glitch that sometimes leaves me trapped. I can exit the build mode but do not regain control of my character. For me, on an XBox controller, I can regain control by pressing the (yikes! I don’t know what it is called) not the little menu button on the right but the other one on the left. The one with the 2 rectangles on it.
I noticed getting stuck way off planet when using build cam in that mode and running it into something, not to mention some insane flickering to go with it. I could exit out again as well as regain control by using ESC or B (PC). Not sure if the same issue. I got stuck in or under a floor once without build cam, but escape with some wiggle and jetpack got me out of that one I think.