Ugh as well! I rarely change papers anymore because mine is so finicky.
Too much of a headache. Just easier to buy several more printers.
I use my P800 almost exclusively with Ilford Gold Mono Silk for B&W prints. The output is superb.
You could try taping a small leader of a heavier paper to the leading edge of the canvas and see if that helps.
A $500 price jump from the P800 to the P5000 but I heard most of the loading issues disappear with the P5000.
Someone that actually has one can elaborate I'm sure.
I think Epson knew the demand would be there for the P800 roll feed and did enough remanufacturing to barely make it work figuring the pros would all go for the P5000.