I seeing the same issue and have been asking around but it appears to be an issue with Mach3 for sure. The odd thing is, at least what I've discovered is the run time is almost identical to the simulated time yet on my runs the time is actually much longer in real time.
To clarify a little more, the simulation time appears to be way off and that number is also about where the clock seems to be stopping during the real run.
One other thing, if this is the case, how can we be certain the runtime on our tool life or other metrics we should be keeping up with.