Disco 2 Manual Front Sunroof

Hi everyone - this is my first post here, after recently joining the Disco 2 club.

I have a little issue with my front sunroof...not the usual leaking problems (although it does every so often!). Suddenly, as in yesterday, the front sunroof has become very stiff when opening and closing it. A significant amount of force is required on the handle to get it to move. I also now find that the tilt lock keeps engaging every time the handle rotates, even when the sunroof is being slid backwards or forwards.

Does anyone have an idea of what is going on here, and how to fix it? I've had a quick look and can't see any obvious debris/dirt on the runners. I've also WD-40'd those areas and have taken the handle off to make sure all is well there.

I haven't been brave enough to try opening the sunroof for years. I wish they had made these cars without sunroofs.

The LR was my Dad's - he had it for 10 years...until recently. He barely used the sunroofs either, that said given the nice weather we have had over the last few weeks I have used them extensively. Fortunately, I've not had a leak as yet even with the heavy rain and thunderstorms we have had in between.

The front sunroof seems a bit more free on its runners now. I do still find that the lock keeps engaging every time I turn the handle though, any thoughts?