Don't go on more than 6V!

Lyon Adaptor module, MM IV and HG440 are running fine? (In this combination?)

Yes, the problem could be inside the München board. It could be a weak power cable (ribbon type) or a loose connection or slack joint. To check this, you could open one of the modules (I would prefer HG440) and measure the voltage with a multimeter (Pin 14 and Pin 28 on the EPROM chip).

Have you tried another board?