How long are you letting them stay in the mold before you take them out? When I got into tail making mode I saw similar things beginning to happen when I was really rolling along. I think that portion of the mold gets too hot and when the baits come out the cooler air causes un-even shrinkage in the thin tail. I'm seeing a little flashing going on there and in this mold I see that too when the mold is getting real hot, regardless of how well it is clamped or with what .