I'm making a Unity game asset with the UMA character system. I already created a base rig with Mixamo auto rigger and tried to add bones that will handle mesh adjustments (size of muscles, translation of vertices, face customization etc). And I have this annoying problem with one. Single. Bone. In the rest position (in which I'm adding additional bones) everything is fine...
But when I switch to the pose position to check if everything works and needs some adjustments bone which is meant to control the bicep/tricep size on the right side is giving unexpected results.
(Don't mind that envelops are pointing in weird directions, they are meant only for handling the character customization system, and they are not used in animations)
What is even more annoying is that on the left side everything works fine. I tried file cleaning, applying all transforms, duplicating bone that is working correctly, checking hierarchy, checking weights, deleting and creating a new bone with a different name... nothing works. Maybe there's something I missed or don't know? I don't like rigging and it's not my forte so I'm assuming I'm missing something.
I'm working with Blender 3.3.0 with no add-ons for rigging.