Blender 2.81 Weight painting bug? Just started using blender 2.81, I didn't see this issue with 2.80. I do weight painting on one vertex group, and it somehow ends up affecting another vertex group.
When I change weights of one bone, it changes another bone's weights. For example for low poly hair, I have bones with weights on, and after doing all the hair bone weights, it completely messes up the main head bone's weights on the hair mesh. What gives? Why is one bone's weight changing another bone's weight?
This behavior is normal for Blender including versions before 2.80.
 
Weight > 0 belongs to new or selected Vertex Group.

One bone can affect different groups with blending by weight by design.