Small clunk and drop on window when rolling down 2/3 of the way

[Xproplayer]

I just swapped out my regulator on the passenger rear door, used the URO replacement, swapped over my motor, the movement was clean when I dry tested it without the motor. But when I lower the window about 2/3 of the way down theres a small clunk and it drops maybe 1-2 inches. Any clue what could cause this? My only idea is the bottom bolt thats connected to the pulley being a bit too tight and the pulley not unwinding.

[Xproplayer]

Update, it now clunks maybe when its halfway down, and smaller. Perhaps my bolt theory was right and the bolt has loosened up? Any ideas?

[oldroller]

you may have glass to channel binding, causing the bumping. Try some spray silicone lube on the channels.
Worse case scenario is a channel that has warped or the metal support is bent.

My rears rarely get used. When lowering to clean, the glass stuck to the upper channel and caused enough load on the regulator
to bust a pulley.
Reminder to self...clean and lubricate the glass channels!

[jclausen]

Sounds like window regulator is dying

[Xproplayer]

Sounds like window regulator is dying

What makes you think that, given that it only happens when going down you'd think gravity would be helping.

[MN2K740i]

My guess would be that the seal/track on the rear window isn't quite reinstalled correctly and it's putting resistance on everything until it has enough force to pull it thru and continue the rest of the way down.

It's the only thing that really makes sense to me.....

I guess in theory (Idk if it's a thing because I buy my regulators with motors, my luck my existing would die a week later lol) perhaps the motor didn't get reinstalled correctly on to the regulator, like the motor's internals aren't sync'd up with the regulator some how maybe? Idk....It's a theory/long shot at best....