We've had our UM2+ Extended for about a yr and it's mostly been great. I've always noticed in the back left corner it curls a bit, but just tended to avoid the area. I've got a bit more time and choosing now to dig into it w/ the help of the experts here :).
I grabbed a test square STL from thingiverse, stretched it out and printed it. The first couple layers are great! However, subsequent layers failed (bubble/ripple effect). I've tried with multiple types of filament, leveling the bed, different glass, various Cura settings and I'm tapped. Any thoughts would be greatly appreciated!