Looks like a pot not reading the full travel.
Try recalibrating, do NOT get into the deadspot when you move the throttle.
If needed go into AH, options, controls, map controllers, select throttle, calibrate that axis only.
And again, when you do, do NOT get into that dead spot. Keep it just short of it.
Then test, see if you can get full travel.
If not, return the stick.