Hi
I can understand.
Try to adjust the tap of primary winding in the main transformer of the machine
2) measure the power supply electronic +5+24Vdc,etc see your schematic diagrams if there in tolerance.
Not more higher than 0.7% or down,otherwise you must repair or replace the electronic board
3) if the voltages fluctuation is very Heavy try to install Relay stabilizer from Heidelberg manufacturer, otherwise you must have many problem like
this..