Dead spot in throttle curve?

[solomon7]

I've got a Futaba T6EX 2.4ghZ Radio.
Recently it seems around 15 to 20% throttle, slowly increasing throttle, that the motor kind of stalls out for a second then "catches up" to where it should be almost a soft jerk.
I've swapped motors, ESCs, BECs and everything else and it appears it is the radio at fault.
Swapped in my scaler's Spektrum DX6 and no problems.
I've calibrated, and it still does it at the same spot on the stick's movement.
Can a radio develp a flat spot in the sticks movement or something? Any fix?

I don't get it, and can't drive my crawler how it is.
Anyone shed some light on what's going on?