I think throwing your hands up when Maya get's it's window focus wrong is totally in order. I've come across this as well and it does seem to be an issue of Maya getting focus wrong.. It's been a big issue with node editor vs bifrost graph editor fighting for focus too. It doesn't operate by magic, but it does operate by…
sounds like an issue of which panel has focus. Dont have maya open, but if you are adding keyframes, the controls would have to be selected. So if you temporarily had focus in the viewport, or outliner, or somewhere that is not the graph editor or timeline, then when you press copy it would copy what is selected - which…