We recently purchased a DL3021 DC Load, when it was powered on, then set to CR, the STATIC indication was on and the Knob and the adjacent control keys are de-activated, the STATIC indicator is now not lit, and the Knob and control keys are active after we tried to change to variable resistance by pressing various switches to see if it was possible, the load it now in a variable resistance mode using the Knob or control keys when in CR mode which we require for our purpose , the STATIC indication is not lit in the CC CV CP modes also, is there a toggle to turn off and on STATIC mode to use variable resistance mode. Unsure what switches we operated to turn off STATIC mode. Cannot find any reference to this in the user manual, and the Rigol help desk cannot answer my question. Our concern is if we do a Factory Reset or Firmware upgrade, we will not be able to select the variable resistance mode.