Cause:
- the DC link voltage has fallen below the limit value for the minimum voltage during travel
Remedial action:
- there is a power failure while driving, check the phase voltages of the power supply
- check the parameter "UDC_MIN" (factory setting: 450 V) in the "Power section" menu 
- check mains connection (mains voltage, line cross-section, mains choke rating, mains impedance)