Adrian: There are four internal leads inside the MCR - left hot, left cold, right hot, right cold, and they correspond to the four output pins at the rear of the cartridge. Electrostatic grounding of the cantilever is accomplished by the act of using metal screws to mount the metal cartridge body to the tonearm.
I am also inclined to think that the problem is more likely to be the tonearm rather than cartridge. If the internal coil leads of the MCR were touching ground, chances are high you wouldn't have any output.
Nonetheless, if by swapping cartridges you can make the problem completely disappear and are confident that the MCR is the cause, you are welcome to send me a message through the forum.
I am also inclined to think that the problem is more likely to be the tonearm rather than cartridge. If the internal coil leads of the MCR were touching ground, chances are high you wouldn't have any output.
Nonetheless, if by swapping cartridges you can make the problem completely disappear and are confident that the MCR is the cause, you are welcome to send me a message through the forum.