With ArduCopter 4.2, you must set H_COL_ANG_MIN and H_COL_ANG_MAX before flying. In Arducopter 4.2, I have updated how the collective is translated to the autopilot from the parameter set up. You now must not only set the H_COL_MAX (maximum collective in PWM) and H_COL_MIN (minimum collective in PWM) but you must also set H_COL_ANG_MAX which is the collective blade angle in degrees associated with H_COL_MAX and H_COL_ANG_MIN which is the collective blade angle in degrees associated with H_COL_MIN. It makes setting defaults for parameters like H_COL_ZERO_THRST and H_COL_LAND_MIN much easier because these are set in units of degrees rather than PWM.
If these are not set correctly before flight, you risk the motor shutting down inflight during RTL or landing in autonomous modes. Also please check you ARMING_CHECKS parameter and make sure it is set to all checks unless you have a good reason not to. The developers put in pre-arm checks that catch things like parameters not being set and you make yourself vulnerable to a crash if you don’t have these checks enabled.