I've never experienced this pitch up problem.
I slow down, when at around 5kph in airspeed, (still have 5-10 degree nose up) i press auto hover. When the nose dips down to horizontal, i press and release trim again fast, to set a new hover point and the heli stays there.
The other way i use is to slow down, when at 1-2kph, i pitch the nose down to horizontal, press auto hover, and she stays there.
post a track and we can see what happens.