[Keystoned]

I'm pretty sure I found the problem. That corner is tricky with the bend, wrinkles and such. So did an unconventional repair there by using weatherstrip and caulking cord, which appears to be a solid version of dicor. Working with it revealed it has the same feel as solidified dicor. So I filled that corner void with it until no more would fit, followed by self leveling dicor to fill the gap between it and the old dicor that was there, if any.
I also stuffed it into any voids along the cap and TPO along the top before covering with more dicor. I only managed almost half along the top before time ran out so I'll do more today in prep for a expected rain this weekend. Fingers crossed that the leak is fixed. I have a large tray on the bed platform to catch any leaks but I hope it will remain dry...