Troubleshooting Mastervolt MICC Malfunction

[Tikitour]

I have a Mastervolt Mass Combi inverter/charger that is controlled by a MICC controller.

A few nights into our first long passage (3 nights total), the MICC panel lights started flashing erratically, like Christmas lights. None of the buttons worked. We were running instruments and electric autopilot so consumption was high, but voltage before sunrise was still ok, 12.3-12.4V. The flashing eventually stopped when the voltage came up with solar charging the next day. For a while the Ah-Time button did not work unless pressed for a while, but eventually returned to normal function and all seemed resolved.

Now, about 4 months later, we are in a marina and using shore power. Fine for a few weeks, but now it’s misbehaving again. Flashes while on shore power, and the Ah-Time button does not work anymore. The inverter and charger (mass combi) are functioning properly, it’s just the MICC with issues.

According to Mastervolt these controllers are not serviceable and need to be replaced. We have found a new one onboard (amazingly) but before I just swap it over I’d like to work out the cause, so I don’t just fry the new one. Has anyone come across this issue before or have any theories on what the error may be?