Oh no, that is bad. I'll get right to fixing that when I have the time :)
Faster idle hitters skillmine bonus breaking the game by being too high was second time I encountered this bug, first time it was cheaper upgrades skillmine bonus breaking the game by being too high (it made all upgrades unbuyable).
Oh, and this might help locating the bug, when I unlock the skillmine and choose the option out of the three offered, I assign workers to a field, however, when they finish that first field, they dont start working on the next one, but instead they work on some extremely easy virtual one, so I have to unassign workers by pressing X and assign them again and give them order in which they will work on visible fields with shift key and clicking, however, when they finish all fields, they resume working on that very fast to finish field that instantly regenerates (or there is infinite supply of them?). I am assuming all of this, because bonus is increasing very fast.