Yep, I took it out and inspected it. The rollers were all still intact and in their guides. The popping sound is made whenever you roll the regulator all the way up to where the glass should be fully seated. When the gear on the back of the regulator makes it to the end of its travel, instead of stopping it slips off the track and the pop noise is the spring forcing it back down. I'm thinking there used to be a stop on the track but the initial loud pop I heard was perhaps the last tooth on the track snapping off.