I purchased this unit used. After much fiddling, I got it to print acceptable results, but I noticed that the wheels on the laser carriage were so tight against the 8020 rail that the wheels would develop flat spots on them after it sat. If you manually pushed the carriage left and right you could feel the flat spots as it would "bump" as it passed over them.
I tried 3D printing some auto-tensioning wheel holders for the bottom wheels on all the carriages, but my results were even worse. I put the unit back with the stock wheel positions on the polycarbonate and I am still getting terrible results.
I am using LaserGRBL but I get the same results with EleksCAM:
Here is the test image:
Can someone please try this on their A3 Pro and post your result, and post your .NC file as well as your GRBL configuration file?