Camera bounces above basement ceiling level?

Hello, I added a basement to my Sims’ existing house. The only problem is, the camera/zoom cannot go past the ceiling level of the basement. If I go outside the bounds of the basement (into the dark abyss), the camera bounces back down to floor level of the basement. But as soon as I pan back over to the basement rooms, the camera bounces back up to ceiling level. I can use Tab to get lower, but as soon as I come out of Tab mode, the camera bounces back up. This is not an issue on the upper levels of the house. Any ideas? I have no mods/cc, and my game is fully up to date. Thanks in advance!