I had problems with sagging roof this summer while I was vacationing in Poland. The sag was more then 200mm at one stage and I thought the roof would break or fall apart. Still, once the sun disappeared behind the cloud, I was able to raise the roof and then lower it all the way down.
Stay with me for this story, because there are things to learn here.
I called around 5 different VW dealers and only one was able to see me on a Saturday that actually sold VW Californias. I drove an hour to Zielona Gora and found my way to the dealer there. They had new T 6.1 Calis for sale there and also mechanics who could look at mine that day. But, as it turned out, the mechanics manager was able to help me out and the solution was quite surprisingly easy.
He told me to open and close the roof 10 times, with a 15 minute cooldown pause after the first 5 times.
He added that new Calis in their showroom have the same sagging roof problem at times and this is the same and only fix they do. It always works. He added that it all depends on the temperature when the hydraulic system was filled with oil. Mine was filled recently when it was around 18 deg C and on the day it sagged the temperature was around 30 deg C.
He also asked me if I recently drove over very shaky roads, because apparently that can result on bubbles in the oil somehow. I said "You mean like here in Poland?" ... and we all had a good laugh.
I did as he said, raised and lowered the roof 10 times, and that permanently fixed the problem.
Now, will you ever see your roof sag? Yes, definitely, but it should only be a few centimeters at most. You fix it by slightly lowering the roof a little and then raising it all the way up again.
On my Cali 2013 SE the roof controller would attempt to auto-fix the problem once in a while all by itself in the middle of the night. How do I know? Because it woke me and my wife up in the middle of the night and gave us quite a scare
The story is long enough. I hope you can fix it by doing what the Mechanics manager recommended.