What happened?
Each of the three stepper motors on the MMU unit is controlled by a TMC driver on the control board. This message is shown in case the TMC driver for the Idler does not have enough current.
How to fix it?
Check the wiring and connectors on the MMU board.
Make sure your MMU3 unit is correctly assembled with the PD-board addon attached.
In case the issue persists, contact our Kundendienst.