I found a burrow and built a lean-to inside of it. I then built a cupboard because I wanted to know if you could put one in a leanto. Turns out you can, but I couldn't take it back out. I wondered if this was a bug so I put a log in there, too. Also can't take the log out.
Thought it might be a Purus Pasta bug, but it also happens in the default client.