During the system monuments, the keyboard is inactive, but at the
pressure of one button all movements are stopped and this message is
displayed.

This is useful in case an abnormal motion is detected, for instance the
column does not stop at the release of the corresponding button but still
continues to move.

Check if one button has been involuntary been pressed and restart the
operation with a new power on procedure.

In case there is a stuck key, one of the previous message E850 and E851
must be displayed, so acts accordingly.