I FIGURED OUT!
I was able to reproduce your error and it’s the same thing I did previously.
Ok when you paint with MRGB without Zadd or Zsub turned on, you paint
the material you got selected on the model BUT the original material also
stays on, so you essentially got 2 different materials.
If you change the Material, only part of the model changes and the part where
you manually painted as MRGB stays the same!
To fix it, you switch to MRGB and turn off Zadd/Zsub and paint with the same
material the whole body. Check the subtool preview and you can see if it’s
working. Hope this helps ^^