2nd Arcdroid, same straight line issues

After going through all the possible causes with Andrew, he warrantied my 1st Arcdroid but the new one has the same problem. Straight lines come out slightly curved. It has the same problem with the stylus or a sharpie so not torch or material related. Calibration is good, firmware is up-to-date. Im starting to believe these Arcdroids are just not that accurate. The curved line is not drastic but definitly noticable. I zeroed both ends of a straight edge and ran the stylus along and you can see in the middle, the values change on the machine. I went through everything with Andrew on the first machine, however, I tried to contact again about the new machine but never heard back. Has anyone else noticed this? I know there are a couple threads about this issue but nothing seems to have been solved.