I can somewhat safely say that the dev team is aware of this, as Kazinsal told me about this problem. What's going on is apparently the devs made a error whilst making some sort of special minable object using the POB system, and its' interacting with the Mining plugin incorrectly.
AFAIK, it only affects core 1 POBs.
Kazinsal had mentioned it but I made Thackeray open a proper bug report instead of bugging me in PM. The dev team 'being aware' of something without it having an open post in the current bug report thread tends to make the thing fall off the radar. ~Alex.