Beds in the lair disappear after loading a saved game

Steps to reproduce:

1. Start sandbox map Hollow
2. Build a lair and get some minions
3. Save the game
4. Reload the saved game
5. There are no beds in the lair, minions sleep directly on the floor

WFTO v1.3.1f5

Lair before save:

After reloading:

A minion sleeping on the floor: