Sunroof not closing completely or popping down when the motor stops.

The nylon pads don't want causes drag.

When mine sounds slow, I clean them. Clean is smooth and fast. And a little lost speed here can prevent it fully closing on a cold day.

Also if you install new sunroof trim on the panel, if its too thick (not pulled a little to thin it out) the roof wont go forward enough to raise up.

There is no Porsche requirement for grease here, thats why they run on low drag pads that simply side, with the block at the end having ANY mechanical effort needed to raise/lower the rear edge. I have some very light oil in there to prevent galling, but thats the only wet part. If the rear is banging around, the plastic caps on the guide and gate guide (sliders) are gone...gotta get a new ones.92856404642 and 92856408343

The nylon guides on the gates, and the slide assembly (92856426702 and 92856426803) are important, often missing or worn..or..gummy and sticky.
That rubber part is a connector, not a clutch.
The actual clutch is inside the gearbox that connects to that rubber.
That screw, which allows people to close the sunroof in an emergency (with the tool), has thin shims under it, which adjust the "clutch" function.
Try tightening that screw, first...sometimes they come loose.

Remove all traces of old "grease". (We remove the sunroof and clean the rails, the cables, and all the other pieces, in order to do this.)

Years of 928 sunroof repairs has found that lubrication of the guides is essential, but any type of conventional grease is bad.

"Sil-Glyde" is your friend....any Napa store or Amazon. Minimal amounts are all that is needed.