[unstable] glow rune not working around mine entrances at high altitudes

[Arium 321]

as title states, when getting close to a not doored mine entrance on unstable 4.00-b50 (ae05ad5) the glow rune attached to my toolbelt turns off.

stepping further back will turn it back on, however regardless of wether its a freshly booted game it will always occur.

the mine door is at an altitude of somewhere over 10000 dirt above water level. i did not encounter this on mine openings, wether doored or not, at low altitudes.