My passenger seat wobbles a few degrees. Before I unmounted it I thought the problem was going to be loose mounting bolts, but they were solid. Instead I found that the bottom-most components of the seat, including the bolt holes and front/back movement screw, are not rigidly connected to the rest of the seat. In the photos below I have pointed with two fingers at two components that I think should be rigidly connected, but instead they can move about 1/4" together/apart (i.e. the seat can move up/down that distance when the rails are bolted down). One of the photos I couldn't fit my hand, so I have a screwdriver shaft from out of frame pointing at the upper component. The problem seems to be the same at all four corners, but I've tried to show them from different angles in the different photos.

I suspect some bushings or bearings have failed here, but I wasn't able to figure out how to take apart the section in question to get a closer look. The big "bolt head" southeast of the screwdriver tip in the third photo seems to be the point of connection, and there's one at each corner, but it spins freely instead of unscrewing, and there's only about an inch deep plastic-housed mechanism behind it rather than anywhere that seems solid enough for it to be anchored to. I'd appreciate any tips or your suspicions before I go further.

I'm not 100% sure what you're looking at, but assuming you're talking about the bolt with a big head that requires an allen key with a plastic bushing around it at the front of the seat, I have good and bad news. The good news is that it is a 10 minute repair. The bad is that the white plastic bushing I think you're referring to has failed, and the only good fix is to buy a new bolt/bushing kit from the dealer for ~$170 for a kit that consists of two sets of bolts and bushings. When it failed on my X164 a few years ago, I fixed the rocking by removing the remains of the bushings, adding something I've forgotten around the bolt that stopped the rocking, but also triggered an airbag warning since the bolts/bushings are part of the weight sensing system in the passenger seat which required a trip to the dealer and an hour of labor to reset. The reset procedure requires putting a variety of weights on the seat to calibrate so it isn't an easy DIY job.

Thanks. I did spin that "bolt" on one of the corners, but it seemed to just spin freely with a small amount of friction, and the bottom of the bolt seems to be inside a plastic housing and not somewhere I can get to the nut or threaded hole it's supposed to be unscrewing from.

It looks like I missed the window to edit my post, but here's my writeup of the replacement: https://mbworld.org/forums/gl-class-...king-seat.html