One of the strips on mine had a couple of places that were bowed out of straight by about 3/16" at their apexes, exposing the glue by that amount. The glue was on the outside edge so it didn't cause a problem, but I removed it anyway with a blade, which I also used to "straighten" the bow. It arrived that way and hasn't changed in the year that I've been using it.
My problem with the D-Roller has been the heavy bar at the core (which is probably the most expensive part of it). Apparently, the glue isn't strong enough to hold the plastic (Mylar?) material against it. I had to remember to keep the edge of my print a couple inches from the core. Much worse of a problem was the undulations on the print caused by the weight of that core as it flopped around, regardless of how slowly I rolled, and how tightly it was wrapped. I finally cut it off and replaced it with a cardboard core from a roll of paper. It has worked fine since then... much easier to handle, the glue sticks to the cardboard core, and most importantly... no undulations. I suppose a length of stiff plastic plumbing pipe would work fine too.
