Ok, got a loan of a buddies drv8825 drivers and tried the coasters again, with the same results. So that ruled out my electronics. So then, it hit me, backlash. I was getting the flats on the sides when motion reversed. So I slowed the code down and then I could see that when there was a change in direction the middle assembly was lagging the outside rollers. So backlash, I’ve since hooked up my old electronics to use linuxcnc to add backlash compensation and I am now getting circles. This is just a temporary fix, I’m going to have to reduce the tension in the middle assembly or rebuild with stainless on a machine this size.
Thanks for all the help the forum has provided.