From the manual ....
If the indicator lamp in the soft top switch flashes while the soft top is being operated,
1. Hook the luggage cover in the boot into the closed position and close the boot lid or unlock the soft top first if being opened.
2. The battery voltage is perhaps too low .
3. The hydraulic pump may be overheated - the soft top may be operated once it has cooled down.
4. If the soft top opening / closing procedure has been interrupted after the soft top switch has been activated , the cause may be an operational fault or a control unit malfunction.
TO RECTIFY THE FAULT , RESET THE SOFT TOP MECHANISM CONTROL UNIT BY TURNING THE ELECTRONIC KEY ELEMENT IN THE STEERING LOCK TO THE 0 POSITION THEN BACK TO POSITION 2.
REACTIVATE THE SOFT TOP SWITCH.
IF THE SOFT TOP SWITCH CONTINUES TO FLASH , HAVE THE SYSTEM CHECKED AT AN MB SERVICE CENTRE.