I posted it as a new post as there was no response to my initial post.
It is not the same issue as the Herelink ground side multiple inflight crash and reboots, A/C Failsafes
In my case the vehicle was in RTL and when the Herelink powered back up it was switched to stabilise a few feet from the ground and ended up upside-down in long grass.
The Herelink did spontaneously reboot - but the main problem is how it powerd back up.