One of the non-power wires to the battery fan seems to be labelled FPWM, that sounds like Fan Pulse Width Modulation. That presumably sets the fan speed. The other is hard to read, and I can't quickly find the original, but it seems to be labelled FRWM, the W might be warning or similar. So I think the BMU is monitoring the battery fan, while the EVECU doesn't seem to be monitoring the main cooling fan. I'd expect the cooling fan to come on only after the on-board charger has been operating for many minutes. My guess is that something is wrong with that fan wiring, so the BMU doesn't think that the battery fan is running, and aborts the charge despite it possibly not needing the battery fan at all. I suppose Mitsubishi doesn't want to start the charge if there is a problem, as the user would assume that once the charge is started, there is no reason it won't finish. Better to be alerted to the problem early, they may be thinking.
It would certainly be good to see a trouble code for that situation though.