I am also getting this error. I was printing and it stopped mid print. Machine totally froze but was still powered on. I had to reboot the machine to do anything and it came back with this error. I have a video of my machine booting with the error.
Exact same error - what I have found out it that many of the Mimaki models share parts.
And on the PCB there are some specific fuses and LEDs that can blow, if fx. external power is unstable.
My hope is over the next days to have time to measure the components on the PCB and hopefully find an error.
What I have found is that the error refer to 42V supply voltage for the main PCB (EPL2).
So I keep you updated here, when I have news