I have a few that are the same way,I now only keep hides that I skin myself,no knife except to get it started at the legs.I have also started using a sander with 60 grit on both sides of the hide and that will thin out the thick areas and also help clean up any slashes. I have used sanding stone but they don't last very long,the sander seem to work better for me, not very primitive , but O well.
Pappy