ahh it's because they have low manas and won't back on those spawns but you can actually change this if you wish, in second action in HuntSemiCircle section there's a line:
if itemcount('shovel') ~= 0 and itemcount('mana potion') >= 10 and spawn ~= 'Semi Circle' then
change it to:
if itemcount('shovel') ~= 0 and spawn ~= 'Semi Circle' then
and it should be done.