You're going to have to backtrack your actions.
Even with THIS game engine...and yeah, I know this is a reach...there's no reason that sort of thing should "just happen" without some cause.
Think back to the last time you saw that game working right. What was different vs now?
I updated Enhanced Blood from 1.5 to 1.6a.
I added Darkwater Crossing Expanded. - Disabled and loaded a save without it on and it did not fix the problem.
Updated 7K Better Whiterun - City Under Construction. - Disabled and made clean save, did not fix the problem.
Updated nvidia drivers.
I think that's it.
Edit: I redownloaded the house mod and that fixed the problem.
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