Issue #23247: WRShacksBase01.nif: gap underneath stairs in mesh
This was originally reported in a placed ref ticket (Issue #23241). I was able to confirm the problem. The particular mesh is very large, but Arthmoor said that we have done fixes for other "megameshes" like it in the past.
It should be rather obvious where the gap is from the screenshot I linked. It's not a huge gap but it is noticeable if you look close enough.