Looking at your print and pictures of the printrbot jr, I think your problem is that the Z axis is not perfectly perpendicular to your X/Y axis throughout your print. Possibly the Z axis mounts are a little loose.
As the Printrbot Jr has a cantilever nozzle mount I think your Z axis leans forward or droops a little as the nozzle moves away from the main support tower resulting in excessive Z-lift at the rear of your printed object.

A non-level bed would explain bad results in only the first couple of layers, not bad results through the whole print.