I was happy to fly my drone but one morning while I was flying at position control mode, the switched to RTL mode, the drone started falling and I couldnot control it even after getting it to manual mode and it crashed. After that I am not able to arm it. It rejects the safety switch completely as if its not there at all. The error is GPS Horizontal Pos Error too high and press safety switch. I am using pixhawk fc and qgc. GPS is neo M8N
So did you try disabling the following two checks? CBRK_IO_SAFETY and CBRK_VELPOSERR. The first disables the need to press the safety button and the second disables GPS horizontal poss check error.
This normally works for me when I try to arm without a GPS receiver available.