Yes, make sure the drains are clear, and also be sure they're connected (the connectors are known to crack or break off entirely). Another thing to do is lubricate the track to be sure it's not sticking anywhere, use a good spray lubricant, not WD-40. Many don't know that you can operate the sunroof manually to be sure it has full travel, just in case the drive motor is stalling out during the closing sequence (this is usually caused by lack of lubrication or a broken component jamming the track).

'99 Disco II
'95 R.R.C. Lwb (Gone...)
;76 Series III Hybrid 109
'70 Rover 3500S