The motors are lead screws driven by electric motors...made by linak.
The little short cylinder thingys near where the crossbars cross are some sort of dampers.....
The best thing to do is get a #2 phillips screwdriver, undo the upholstery around the mechanism and take a look at what's going on when it's going up/down. It's quite easy to peel back velour and take a look..
There are a number of poorly designed/executed weak points on the SMB lifting mechanism, for instance, the crappy pivot bolts in the crossbars. There are a number of threads here about upgrading this hardware.
Do you have anything on the roof? If you have stuff up there, you may need to tighten your springs....
Here is a picture of the Linak actuator from Bmerrit's power top: