The solution to this is simple, turn up the heat on your bed, i had similar problems in the past, but then tried to print at 120c, it worked like a charm, the plastic keeps softer then, and does not "collect" the warping forces in the print.

i set my first layer temp to 100c and the other layers to 120c, that way i dont have to wait forever for the bed to get to temerature and the printing to begin.