Devon poptop fabric degradation

[DevonAid]

We've noticed our Devon poptop fabric has suddenly and significantly deteriorated recently.
To the untrained eye it looks like rust contamination, but there's no metal (and certainly no rusty metal) anywhere near. It feels slightly tacky to the touch; inside looks completely normal.
We've tried cleaning with all sorts of fluids with no effect. We also use an additional blackout cover over the poptop fabric when camped for more than one night, which should protect from UV damage in my view.
Aside from looking naff, my concern is the fabric will suddenly fail, rip or become a hole.
Anyone else experiencing this, and/or finding a fix?
Thanks!

[Oldiebut goodie]

Possibly tree sap?

[DevonAid]

Thanks, but it appears the fabric is degrading in some way, and I can't think of the last time we parked or camped under a tree

[icosahedron]

Brown mildew/mold?

[DevonAid]

Thanks for comments, appreciated.
We've tried cleaning with all sorts of fluids, with no luck, so would be surprised if it's mould; however it's slightly tacky to the touch, and we notice the problem area is getting larger each time we use the van. Could that be a mould thing??
Might get some mould spray and conduct further research....

[crazydiamond]

Yep im afraid its age degredation. I had the very same thing happen to our devon some years ago. Cant be fixed, I had a new roof bellows made by a guy who I dont think is around now cant remember the name but will have a think. He was in Upton on Severn did upholstery mostly but did a brilliant job.

[DevonAid]

Thanks for feeding back your similar experience.
Did your pop canvas fail completely or did the look of it drive you to replace it, presumably at quite a cost?
Good to know it can be (hopefully) replaced at some point.

[crazydiamond]

It didnt fail but was just sticky and looked really bad. I think it was something around £600  but that was some years ago probably 15years ish

[DevonAid]

Thanks for the further feedback, very helpful