I'm having trouble X-Mirroring or Topology Mirroring vertex weights of a mesh when I use the Weight Gradient tool (AltR click and drag) in Weight Paint mode. I have symmetrical bones on my character, with mirrored names (Left bones have .L , Right bones have .R). However, the problem persists and I have no idea what is wrong. Could it be a problem of having different "Bone Groups" on each side? or something else?