@Jano1 - I had a look at the code and from what I can see it's missing the part which makes the mining radius visible.
@ judos - Try adding this part to your code for the miners:
radius_visualisation_picture =
{
filename = "base/graphics/entity/electric-mining-drill/electric-mining-drill-radius-visualization.png",
width = 12,
height = 12
I am not sure if it's going to work, cause your mods has no entity.lua file. I presume that robotMiningSite.lua & robotMiningSite - large.lua are your drills.
Hope this helps and best of luck.
P.S I am going to give the mod a try, it gives a new perspective to mining.