Carnage,
Thanks for helping us understand how moisture got in there from the get-go..
Yeah, you need to really keep that cargo cover dry, whenever it gets wet..
I believe that the insert between the top and bottom of that cargo cover might be a type of fiberboard material, that could be soaking through and now you see what that looks like from the bottom, unfortunately..
What APC are you planning on using on the spots ? I don`t believe it will hurt the glue if you don`t soak the heck out of it and cause that board to absorb a lot of it.. But it also may make the issue worse, if it indeed is caused by too much moisture in the board..
I always like to approach these challenges with using something really small on a small spot, to see what kind of reaction I get..
You will always be better using something white, so that you can see what -color- is coming off from that test spot.. 1 - Q-tip even, but a small, white, clean, no dang fabric softeners, etc., in it, just a white clean, towel for application and removal, is what I would do if your vehicle was in my Shop..
I also vote -No- on using any type of hydrogen peroxide/ bleach on there..
You are making progress ! Keep going forward ! We are here to help !
Dan F