Sorry for not replying sooner. Don't come here very often.
I am right in the middle of the process today, re: your question. I picked up a brand new unit a month ago for a very good price. Now I am trying to remember all of the stuff...
I came here to look at some of my older posts when I was having trouble updating the firmware a few years ago. I am having the same problem today...
I think I will remove the other unit from the NC50 and just put one new unit back in. It does allow multiple controllers and I recall they co-exist fine.
But I am having some issues with the current Q50 and not quite sure if it is the controller or the NC50. I'm leaning toward the Q50 being the problem.
So, off to review why I am having trouble with the firmware update. The new unit has old firmware and I seem to recall having a similar problem a few years ago, which I was able to resolve and I think I left some notes in a post back then. Some of it may have been due to Win 10, not quite sure...