Hard Knocks, thanks for posting this. I think it may indeed be the explanation for what I thought was the transmission popping into neutral the few times it happened to me with my NX4510HST cab. Last night I spent 45 minutes grading our access road and did some experimenting. Pressing simultaneously on the forward/reverse pedals, even lightly, caused the HST to go into safe mode and the Calibration light to come on as you describe. I then had to wait a few seconds before either pedal would make the tractor move again. It was only about three seconds,
but if, in the meantime, I pressed either pedal, safe mode would not clear until I kept my foot off the pedals for the full three seconds. It is easy to see how this could produce an endless cycle for a few moments, as the tendency is to keep trying to nudge the tractor either forward or backward while fiddling with the range selector lever.
Thinking back again on the few times I thought the tractor was popping out of Mid range into neutral, I now suspect this is what was happening instead. Unlike in Eric's case, I heard no sound to indicate the shift lever actually moved. And while I wasn't looking at the shift lever as it was happening, it seemed to be in the same position the whole time, and the range indicator light on the instrument panel continued to display "M". In a post above (#1101), I noted that raising and lowering the FEL allowed the tractor to start moving again, hence my speculation that this might be related to hydraulic flow. Now I suspect that just keeping my foot off the F or R pedals while I worked the joystick was actually what cleared the condition, just by allowing the safe mode enough time to clear!
This morning I went through the owner's manual for the NX seriein your 2016 0ist s to see if there is any mention of this "safe mode" feature. Nope. I only saw only one reference at all to the Calibration light (in Sec. 4-19), and even that was simply to identify the light on the instrument panel. Nothing at all about what the light means if it comes on. Sec. 4-16 identifies the Calibration
switch, located on the right-side fender cover, but says only that "The switch is to calibrate response of HST. Only for service," and says to contact the dealer "if you need to calibrate the action of HST."
Hard Knocks, do you know if the "safe mode" feature that we're talking about is new with the NX series? Seems to me this is something that Kioti should add to future printing of the owner's manual. Probably even worthy of a "sticky" on TBN's Kioti forum.
Time will tell if this is really the answer to the "popping into neutral" issue in my particular case. But seems to fit.