Meshparts that have recently been uploaded to Roblox will now break if they are exported back as .obj files. It appears to be the normal model with a decimated version merged together. I have reason to believe that this might have something to do with RenderFidelity.
Meshparts that were uploaded prior to this update are not affected by this.
I hope this issue can be resolved soon, as it causes complications for Vesteria asset development, given that all models i require for renders are stored in Studio.
It might take us a while longer until a fix is ready. Here’s a work around you could use to remove the current blocker on your development workflow until the fix is live.
Apply a temporary texture before exporting, which can be removed after reimporting.
I am seeing this bug happen in a more general case:
I create a new model in Blender, and export it as and FBX.
I import the FBX model into a MeshPart in Roblox. The model looks fine when imported, but as soon as you hit Play, the model becomes distorted similar to above. (It does look like the normal and LOD resolutions are munged together).
But if a apply a texture to the MeshPart, then the model looks fine without any errors.