The very first thing is check your lot traits to make sure one of them isn't responsible. For example: If the mascot is also a vampire, you may have the lot trait vampire nexus. If none could be the problem, go to next thing.
Go to manage worlds, move your sim out. Then select the house and enter it in build mode. Copy the the house to your library. Then delete the house. Move your sim back onto the property, open your library in the gallery and put the house back.
Hope it helps - good luck