Just updated from 1.2.2 to 1.4.9. Under precise/normal/rapid speeds , Gsender has NaN for speeds. When I go to normal mode and set that to 2500 mm/min, it stays and jogs at that speed. If I switch back to rapid or precise the numbers are again Nan. In other words they can be adjusted while on that mode temporarily. As soon as another mode is selected all speeds are reset to NaN and moves at what I think is the slowest jog speed.
Anyone else getting this odd result?
I realize now that I had to reset it in Firmware tab. All good now. Can close.
I see that you have this figured out, but on reading your post I’m the one that’s confused! 
Here’s what I’ve always considered NAN in programming, but you’ve implied a different definition that confused me.
In computing, NaN, standing for Not a Number, is a particular value of a numeric data type which is undefined as a number, such as the result of 0/0.
What values were (or were not) there that you considered NAN? I’m just curious because generally speaking NAN is used to generate an error that can be trapped when an operation attempts to produce a not real value.