Some work fine but others don't it's very inconsistent.
I select the mesh, set the adaptive metric value to 0 otherwise it crashes.
Plug the aiUsetdata into the shading engine, and select mesh, arnold tab, utilities, render selection to texture.
Select location to bake to; pick a resolution of the map to 1k, 2k, or 4k
and tick UDIM's on.
then bake.
Procedures is okay. Try exporting each mesh separatly instead of bunch. If you need script, I can help u with that. Or may be its ur shading network. See if you could send me a demo file gshankar165@gmail.com
if your mesh object rigged to the an object like nurbs circle, you can do seperate from paranted object. it worked for me.