Erratic window behavior, including door bulging

Recently the rear driver side power window of my 2010 Prius started behaving erratically and I'm trying to determine why.

It started with an audible and alarming "thunk" noise when a passenger tried to roll it down. When they tried to roll it back up, it would go a little ways, and then stop and reverse a short distance on its own. It did this several times until we finally got it fully rolled up.

Now it rolls up and down, but every time it does so the inner door panel visibly bulges or moves in and out as the window moves, as if the window mechanism is actually pushing on it somehow.

Possibly related: when we first noticed the behavior, we also noticed that the "window belt molding" (aka weather stripping) had rotted and become dislodged, and was actually sticking to the window and getting pulled out of its little recess as the window moved.

My best guest is that the weather stripping rotted, and part of it has now become somehow lodged in the window mechanism. Although it doesn't _look_ like any part of it has fallen into the window. I've order replacement weather stripping for now, and might get a better look once I go to replace it.

Does this make sense to anyone, or does anyone have other ideas about what might be going on here? Especially the strange bulging when rolling the window up and down.

 

I pulled off the door panel and still couldn't make heads or tails of what's going on

Without the panel on, the window operates perfectly normally.

As soon as I put the panel back on, the top right side of the panel pops out of place (maybe 3/4 inch) when the window first starts to go down or up. But for the life of me, I couldn't figure out exactly what it is causing it to pop out. My best guess is that something is binding, maybe the weather stripping / inner felt liner, but it really doesn't _look_ like there's anything wrong with it.

Fortunately we don't have many passengers so I guess I'll just stop using that window, I'm not sure what else to do at this point.

 

Well it seems like I've solved the problem, although I'm still not exactly sure what the cause was.

I replaced the rotting belt moulding (the external window weather strip), and afterwards the window went more or less back to normal. It still bulges a little when moving, but no more than on the other side. I'm going to assume a little bit of displacement is normal. Most importantly, the alarming "clunk" noise is gone.

I'm assuming something about the rotting moulding was binding with the window when it lowered, although it's not clear exactly what. As much as I'd love to understand better, I'm just happy that it's fixed!