I was just there and I rebuilt my entire sunroof from the ground up.
1) Even though he lubed the cables, there is a solid "crisscross" guide that the cables feed into. It sits in front of the motor. As the motor spins it feeds the cables in/out of this guide tube. The tubes can have rust/debris that can really hinder the cable's motion. Was that pulled and cleaned out? My cables were actually fused to it, I got a used one from Porsche, since the same part and cheaper than BMW. Also if the curved ends are bent even a little, you can see how that would offer resistence to cable motion
2) If your headliner is knew, the aluminum tracks rest on top of this (headliner folded in around the opening) and are pushed up. This, with the new cover over the sunroof itself, they are pushed together and create a lot of resistance to motion.
3) If they put insulation/foam on the roof under the headliner, this may come down far enough to impede it's motion. Not likely, but possible
4) Uneven rise when closed. Make sure #10 exists on both sides.
Bfeng was at my house asked me why I had 30lbs of weight on my sunroof (on tons of towels of course).......................well that's why. To compress the new headliner on the roof and opening.
There is a product called slideeze, it is made for old furniture where draws slide wood on wood. It is paraffin based. I also put some of that on the sliding roof along the edges.
I love my E9 but when I saw the electric sunroof, I knew it was going to be a PIA.