I knew the front passenger window regulator was failing so when the day came and I heard that gunshot popping sound I wasn't surprised. I picked up a new britpart regulator, swapped the motor and installed. Testing a few times confirmed a window that went up and down perfectly. The next day, I was so happy with my work that I roll the window up and down a few times. On the second to last time, I noticed that on the way up the window alternated speeds fast/slow. That's odd, I said to myself and then rolled the window down again. This time, when I went to roll the window up, I heard a new, grinding sound. Like the motor was stripping its gears against the regulator. The best way I can describe the sound is like when you drive screws into wood and then the torque sensor on your drill stops you from screwing in any further. The window refused to roll up. I took everything apart. I removed the motor from the regulator and checked everything. It all looked good. I reassembled, leaving the door panel off this time. No dice. I noticed that if I put my hand on the glass and pulled up, I could slowly force the glass up. it's almost as if the glass is rolling up crooked and getting jammed. I don't know what I did wrong. The teeth on the new regulator looked good. The motor seemed to mesh up well to the regulator. And it all worked well for about 18 hours. What am I missing?