w210 Sunroof dropped

[Frankie]

As it says in the title,my sunroof appears to have dropped slightly at the back. It doesn't leak but I imagine with time it will drop lower.
Is it more likely to be the surround that has dried out and deformed or a fault with the mechanism?

 

[Frankie]

Cables replaced and it worked for a bit and then back to the same problem.
The left cable seems to jam up somewhere above the right side sun visor.
Any ideas?