mystery artefacts...

[aegir71]

Hi, I am milling machining wax using 0.5 mm single flute up-cut and I keep getting these artefacts appearing in the surface of the wax (see pics) They are basically regular holes dug into the wax, the odd thing is that they only appear after type or features to the right (x+) of these feature and usually , but not always, at the top or bottom of these features. the wax is being cut at rates and speeds that does not melt it or I would blame clogging..