I not sure , my last time play game was 10/29 , I think I can create a map to try this problem again ,if still have bug , I will give you the map .

I tried many times I know how could let this show again ,

if your Room build on the map edge . ( i am put dungeon heart at (0,0) ) ,  wait a few time ( 5~10 minute )  it will happened ,

some unit will in unknow block .