I am using a Smoothie 4x board running my three axis CNC mill with a 52 inch by 52 inch cut envelope. I have one X axis stepper, two Y axis steppers and one Z axis stepper. The X and Y NEMA 23 (3.5 amp) steppers are being driven externally with 2M524 step drivers and the Z axis is being run with the Smoothie step driver.
I have worked very hard to get rid of mechanical backlash with decent results. Now I am fighting something that looks like a software controller issue. On some of the paths the router appears to start or end slightly off path by maybe half the width of the router bit. The GCode is generated by CamBam. None of these overcuts appear in the CAD artwork or when simulated by Camotics.
One other data point to mention is size. These jobs are around 24 inches by 24 inches. I don't know if Smoothie has any issues with large-sized 2.5D GCode files.
My Smoothie is running the latest firmware as of late November. I updated the config file as well.
I have a Google Drive link that shows some pictures that highlight the issue and the GCode file of the job. For some reason I can't put the URL in this post. If someone can suggest a way to share these pictures and the GCode file I would appreciate it.