sticky brown residue on top of intex easy set pool ring

This year for the first time after removing my pool cover after vacation there was a strange brown sticky residue
on the of the pool ring all the way around the pool. I have an Intex easy set 18 X 48 pool. This has never happened before. This residue is not mold and can not be scraped off. We had to go on vacation again about a month later
and put the cover back on .. Now the residue is even worse. Has anyone ever experienced this and can it be cleaned?
Seems like the liner is ruined for good.

I'm trying to think of what it could be. Is it from where the cover contacted the inflatable ring? Or at the waterline? If it's from where the cover contacted the ring, then there's probably something eating your cover and it should be discarded. Not sure what you can clean the residue off with that won't damage the ring, though is sounds like tree sap.