Weight Paint adding to wrong side of mesh, subtracting from active bone I'm weight-painting a dog mesh, but the "Add" brush is subtracting from the spot where I click, and instead adding to the corresponding mirrored part on the opposite side of the mesh, over the Y axis. The problem becomes worse as I approach the crease between the selected leg bone and the underbelly, and doesn't seem to be a problem when I am painting the leg itself. 

Weight paint was working fine yesterday, and since then I have made edits to the armature and reapplied the "symmetrize" function more than once. I haven't made any changes to the painting options except to make my brush stronger.
This problem was solved by clearing all transformations made in pose mode and then returning to weight paint mode. I don't know what exactly was causing the problem or happening however.