How exactly do you have the steppers wired (e.g. one per driver chip or wired two steppers in parallel to one driver chip).
So it does not do this if you disable the Idle Current Reduction? (install J4 to disable this feature), CORRECT (please confirm).
From the instructions: “Idle current reduction MAY cause lost steps IF your software settings are very aggressive for the start rate and accel rate. It takes a few microseconds to restore full power when commanded to move from an idle current reduced condition. Experiment a bit with this.”
BrianV