Same for me, map generated in A20 b238 but updated to 20.1. I've tried to even start carrying 3 robotics and 1 sledge for BM. Well before the end of the night they all have fallen and are inside the last player built block resting on soil. Don't seem to fall farther than the soil though.
Did try recreating something similar in a A20.1 generated map and couldn't really reproduce, seemed to be a bit more... sturdy but not really sure why that would be the case. May get tired with my A20 map and just start fresh to see if it is actually better.