Rear window regulator

[zach_carver]

Hello guys I come here looking for some help maybe? I have a 1976 chevy k5 blazer with a manual rear window of course. Well ever since I've owned it when I roll the rear window up it would pop the outside seal out of the tailgate when the window was almost to the very top like something was pushing it up and put. Fast forward I replaced the seals in the top and tailgate with precision gaskets since then. In the meantime I also had to replace the rear window regulator because it stripped out a few teeth off of it trying to roll it all the way up. Well a few weeks later I've stripped out another regulator in the same spot same teeth on the regulator. Has anyone seen anything like this. I removed the seals out of the top to make sure nothing was binding but it didn't affect it. Could my crank be bad stripping out these regulators? I know this is long winded but I wanted to provide all the info best possible. Thanks guys