Hi i have a cnc router that is from china, yes i know is from china the quality is not anywhere but i dont buy it i recive it like a payment from a debt that somebody owe me, the machine is having a issue, when you send a square to cut, at the end of the cut in every single side of the square the machjine cut in the inside of the square leaving not a 90 degree corner, i attached some pics of the issue.

the software im using for cad is aspire, the type the g code that i save the file for use the machine is Mach2/3 Arcs(mm).txt and the software that i use for reading the g code is mach3. i use on pc for the cad software and another pc for the mach3.

hope you can help me to find out the problem of my machine and thanks in advanced.