I had a similar problem with Marlin 1.1.6 while flashing MPX.3 and a Base v1.3 controller.
I re-flashed the Firmware and Reloaded firmware defaults from the EEProm. Using M502 - Factory Reset and M501 - Restore Settings and Saved with M500.
Now I made this sound simple! This was not a simple process As the original flash Arduino IDE refused to allow me to re-flash the controller. So I reverted to an older version of the Arduino IDE Flash an older version of the firmware, then proceeded to upgraded back to the Marlin 1.1.5 with the newer version IDE as that was the firmware that had previously functioned Best for my purposes.
This did not happen with the first flash and I was about to give up and purchase another Controller!!
When is finally accepted the flash of the older version Marlin. After I verified it worked then I re-flashed with Marlin 1.1.5 Using a Newer Version of Arduino IDE.
I re-flashed the Firmware and Reloaded firmware defaults from the EEProm. Using M502 - Factory Reset and M501 - Restore Settings and Saved with M500.
Now I made this sound simple! This was not a simple process As the original flash Arduino IDE refused to allow me to re-flash the controller. So I reverted to an older version of the Arduino IDE Flash an older version of the firmware, then proceeded to upgraded back to the Marlin 1.1.5 with the newer version IDE as that was the firmware that had previously functioned Best for my purposes.
This did not happen with the first flash and I was about to give up and purchase another Controller!!
When is finally accepted the flash of the older version Marlin. After I verified it worked then I re-flashed with Marlin 1.1.5 Using a Newer Version of Arduino IDE.