Hello. r868
After this error, I saved and downloaded the game. One of the blocks sometimes becomes inaccessible. The building cannot be complete.
hotkey_save.zip (4.8 MB)
Put a ladder up to it, sometimes they need some help reaching :).
There is already “native” ladder on the first screenshot
Tried it, didn’t help the building still cannot be completed.
That ladder is too low, it has to reach the inaccessible block.
Are you running the latest update? This should have been fixed already 
You’re just going to have to keep dropping ladders. I don’t know why it’s happening it should have been fixed in the latest.