I've only fiddled with one, tracking a similar problem. That was a bad ground on the light. But although I didn't look into the controller closely I think many outputs - maybe all - are solid state devices not relays. The troubleshooting guides say to use filament test lamps not LEDs... pretty sure sign of a transistor output.
These transistors - whether junction, FET, MOSFET, whatever - are susceptible to several dangers that relays don't care about.
The little indicators can be fed from before the output device, be lit without the actual output being live. I haven't found any circiit details for the m.unit. If the idiot light is on but you have no voltage on the output... something has failed in there. Solenoid control is a problem for transistors because of the inductive kickback voltage. It is easy to protect against in theory but the protection devices can also fail. A relay will get damaged contacts from kickback arcing but it takes a lot of use and relays tend to be cheap and replaceable. One voltage spike can kill a transistor instantly, often difficult to replace (or actually be designed to be impossible to replace... hello Apple...).
I appreciate the many benefits of the m.unit but I'm a cantakerous old bastard and strongly prefer actual switches. I have a newish car with everthing CANbus and 10 computers yakking at each other but fondly recall my 70s first car that I could actually fix with simple tools. I have no desire to take my old bikes, remove their simple switchgear, and add a black box electronic geegaw controlling everything.
