It seems that the stone does not ignite when near Scartalon ridgeline in H9. When i move it south it will ignite but there’s an area from the border to the bottom of the ridge where the ignition won’t happen.
Same bug happens to me in a few spots I tried. So much for my snow castle… I am on top of the Snowy Mountains near the green wall I might add. Coordinates are upper right portion of C-13. Has nothing to do with your position with this bug I noticed as well. I’ve tried going ghost even and can’t ignite it. That’s just one location I’ve tried there are a couple others too.