I am a college professor and I have been teaching music technology since the beginnings of midi. I have run into some interesting technical issues over the years, but this has got me stumped.
My old controller keyboard on my personal, extensive 3-computer studio has always been missing a midi signal on F# 4 --- figured it was a bad contact. I liked the old keyboard, so for the last few years I have always had to put in an F and sharp it later! (Amazing what you can get used to.) Weirdly, even quickly transposing the keyboard would not allow me to get that pitch entered. I guess that was significant, but I didn't really think about it.
I finally bought a brand new controller keyboard and hooked it up. Much to my total shock, the F#4 is STILL DEAD. Every other pitch works, just like it did on the old keyboard. Doesn't matter which piece of equipment I send the midi signal to, it is dead on that note. My midi hub shows no signal at all when I play it.
How can that be? Midi gremlins in my house? Should I consider moving?