Stiff insect screen on Seitz/Dometic skylight . (1 Viewer)

[1881TB]

The insect screen built in to the Seitz roof light above the cab on my AT Comanche has become quite stiff. I used to be able to slide it to and fro with one hand and little effort but now use both hands or have to make a proper effort with just the one. The blackout part of the blind still runs smoothly. I've tried a bit of silicone lubricant spray on the runners but that hasn't helped. I can see that the blind runs on strings and suspect that they are the problem but there is nothing obviously wrong with them as far as I can see. It's a concertina/pleated type blind. I'm loathe to start taking it apart in case I can't put it back together. I could just live with it but I thought I would see if anyone out there has dealt with a similar problem? I have had a search on the forum but haven't found anything.

The screen used to be much less stiff but I'm not sure what caused the change - possibly having the skylight open and insect screen closed on a (mildly) windy day... maybe a bit of debris trapped somewhere...