I had the same situation with my Zero V Xtreme. I replaced the Spektrum RX and the glitching stopped, but I did have to completely setup the ESC again for it to find neutral properly and read '0'. I would turn it on and it would be at 30 or so until I did a complete reset.

No more glitching with the new RX. I was also using an Airtronics servo.

Whip out your manual and reset it!