Why does this happen whenever I put a humanoid in a model?

[z_papermoon]

Randomly started to happen to me https://i.imgur.com/Gd5Aru1.png. (solved)

[mothmage (moth)]

This is a known bug, you won’t have to reimport everything once the fix for this is toggled on.

See this thread for updates on it:

Humanoid causes serious mesh deformation issues

Hi, there was a fix for these released last week but it led to some crashes, so we disabled it. New fix is about ready, we’ll try to get it out this week or it might go out next week. You won’t have to reimport the affected meshes.