Storm32 gimbal via MAVLink weirdness - angles don't match

Morning! I connected a Storm32 gimbal via MAVLink to Copter 3.4.3 and I’m seeing some weirdness. Basically, everything works but the angles don’t match. E.g. when I’m telling the camera to point 90° down, it points a little backwards, more like 100°. Same with pan. 90° left/right is more like 100° left/right. Not sure, where to look for the issue, Copter or or gimbal FW.

@olliw42 any ideas here?

A copy of the PixHawk and of the STorM32 parameters would be helpful. Also which version of both is required.

Pixhawk (Copter 3.4.3):
SERIAL4_BAUD,115
SERIAL4_PROTOCOL,1
MNT_TYPE,4
MNT_ANGMAX_PAN,14000
MNT_ANGMAX_ROL,4800
MNT_ANGMAX_TIL,9000
MNT_ANGMIN_PAN,-14000
MNT_ANGMIN_ROL,-4200
MNT_ANGMIN_TIL,-9000
MNT_DEFLT_MODE,3
MNT_JSTICK_SPD,0
MNT_LEAD_PTCH,0.00000000
MNT_LEAD_RLL,0.00000000
MNT_NEUTRAL_X,0.00000000
MNT_NEUTRAL_Y,0.00000000
MNT_NEUTRAL_Z,0.00000000
MNT_RC_IN_PAN,13
MNT_RC_IN_ROLL,0
MNT_RC_IN_TILT,14

Gimbal V0.96 - MAVlink heartbeat activated, nothing else changed.