Hold it!!
I had the same problem, hmm, I still have the same problem.
The left side of the roof drops down, especially when raised in warm weather, when it cools down, the left side drops. Pumping it up and down untill you don't hear the air circulating in the pump when you operate it, will temporarily solve the problem, untill the next sunny day.
I changed the left ram, as I was not seeing any leaks, but that didn't solve the problem. I only see yellow cristallized substance on the right ram, but I have no problem with that side.
My guess is that the valve block on the motor for the roof doesn't hold the pressure anymore. When it is hot, the oil expands, leaking the oil internally back in the reservoir on the motor. When the oil cools down, it shrinks, making the pressure drop on the affected side.
I am waiting for my "new" second hand motor, to keep my roof closed when driving, so I can (get my) repair(ed) original motor back in place.
A new motor costs € 1400, as you can't achieve the valve block alone. You can get the oil reservoir, you can get the electric motor, but the valve block comes complete with those 2 other parts.
Thanks VW!!