I have a similar problem in my IFS steering box, although mine is harder to turn from about 1/2 turn right of center to full right lock. Turns easy lock to lock going left and from left lock to center going to the right. I suspect it is in the steering box, possibly a seal that is leaking or has disintegrated and is blocking an internal valve. I have the seal kit and just need to find the time to tear into the box and re-seal it.