Loftur TF3LJ/VE2LJX released a new firmware version for the Automatic Magnetic Loop Tuner. You can find it at the bottom of his web page: https://sites.google.com/site/lofturj/to-automatically-tune-a-magnetic-loop-antenna
Firmware version 4.09 fixes stepper motor hiccups that might occur when you move the stepper motor a lot at high speed forward or backwards.
The PCB’s I designed earlier for the DRV8825 or A4988 stepper motor drivers are compatible with this new firmware. I recommend upgrading to this new version if you are using one of mine PCB designs. In the rare case where you would encounter issues, you can always revert back to firmware version 4.08.
Update 2020-06-21: Version ML_v410 was made available by Loftur to adress the issue described in this blogpost.