I’m using Arducopter 4.0.3 with a Herelink HD. I only can arm the drone with QCG (not with sticks) in Alt Hold mode. (throttle too high when I try in Stabilize in QGC and nothing when I try to arm with sticks in any mode). Here my RC3 values:
RC3_DZ,53 RC3_MAX,2000 RC3_MIN,1050 RC3_OPTION,0 RC3_REVERSED,0 RC3_TRIM,1500
With a Taranis Xlite I can arm without any issue.