Very interesting - thanks for the info.
I also have spurious warnings / over-limits from time to time. Through experimentation I have found that applying the rotor brake later than -10 from the stated application rpm can sometimes (not always) generate a spurious report of rotor over-speed (clearly spurious, as it is timed at 0.0 sec at a speed sufficient to hurl the blades into low orbit. The secret seems to be to apply rotor break just below 120 rpm and keep it fully on through the 110 - 50 range. Actually, I keep the break on until the rotor slows and I can position a blade to the front. Since adopting this technique I don't remember seeing a false rotor over-speed warning.
I haven't found the source of the spurious "Gen out of parameter" warning on start, not being prepared to play with the start sequence, but this could be the NiCad, like yours. My 120 does start well, and only once has she "hung" at 400 degrees (aborted, give it a few minutes, next start was perfect), and only a couple of times have I aborted start for battery voltage drop (I give up at seeing +1v to the stated 15v and go get ground power).
Interestingly, I had noticed that the faster / better the start goes on internal battery the more likely the spurious GEN warning is to arise, which is the opposite of what I would expect from a true warning. It is certainly not linked to a low voltage reference on the screen (which we all watch closely during starts) as the false report seems to be less likely to occur if there is a larger voltage drop on the battery. And, I have not actually had a false warning at all when an external ground power source has been added, which would be occasional (I know) but it would then be a cold / first start which would for me be quick and hot per the book; just the type of start that on internal battery only is more likely to generate a false report.
I do always check the on-board screen after the flight just to make sure that it is not a real fault detected; can't bring myself to not check even when I think I am certain the report is false!