Hover issue with new VTOL; Tricopter tilt rotor

Hope there someone out there with Tricopter tilt-rotor experience. I’ve set up my plane with two tilt-rotors in the front, one non-tilt in center rear. Followed all the settings/parameters for vectored yaw and tilt-assist in FW flight. Everything seems to be working correctly on the ground.
In my first hover test, the plane lift off vertically in QStabilize (no oscillations) but immediately drifts forward at about a meter/sec. If I pull back on the elevator to force the nose up, it does not respond, and I cut the throttle to set it back down.
I’ve checked the CG and the AHRS level, and they seem fine. Other thoughts that I could use suggestions on:

  1. I don’t understand how the motors maintain pitch in hover…do they only speed up and slow down, or should they tilt as well? I know they should tilt for vectored yaw in hover. What about maintaining pitch?
  2. If the front motors do NOT tilt to maintain hover pitch, is the most likely problem is that the front motors are not perfectly vertical in QStabilize, or they are not generating enough thrust?
  3. Can this relate to a PID issue or motors gain issue?