I've been using two De-Rollers for a number of years and of course this same problem has been evident with both. I've done the peel and re-stick procedure a couple of times and then I decided to take the fix a bit further. The last time I had to peel the strips and redo them I put a couple of staples through the strips near the core end. That seems to help keep them from migrating in one direction at least. I'm about to do this again soon and I think I'll try a few staples along the length of the strips as well. Since the paper fits well within the strip path the staples present no problem.
I've checked the Bienfang site a couple of times within the past year and the De-Roller is no longer listed. I believe Bienfang bought the product from the original designer and they were the main distributor, but it would seem that they have given up on it. As a matter of fact it would appear that Bienfang has miraculously morphed into a company by the name of Encore Products, so, who knows?
There have been homemade devices described on this forum and others and I may try one of those myself eventually. I do a lot of roll printing, both RC and otherwise, so some sort of de-curling device is a definite necessity. However, you can try the staple procedure for now. It does work and helps the adhesive do its job.
Gary