If you print the same circle part in the center of the bed, is the crease the same as if you print it at either end of the Y travel?
The first time I built the Y bed, the smooth rods were skewed ever so slightly. The Y travel was smooth in the center, but started to get stiff at the ends because of the skew. It was fairly straight forward to straighten out once I realized what was going on. FWIW, I wrote up some steps for the Y bed.