SO, at that line of code, it just started plunging 25mm too deep?
No, I've never heard of or seen anything like that.
You should never use the computer for anything else while Mach3 is running. It can definitely cause issues, but I wouldn't expect it to do what you're seeing.
And no, the screenset has no effect on Mach3 operation. The only thihg different is the look. Everything "under the hood" is the same Mach3. I created the Aqua screenset, btw.
It seems to be related to the high speed movement when it lifts, repositions for the next cut and then plunges again. Yes, your interpretation is correct. It seems to react violently to the F1000 feedrate and then plunge another 12mm or so before happily carrying on with the program running in the window and the DRO updating to the wrong position. If I then stop the program and tell it to go to Z0, its correct. In other words, this is not a case of the machine losing pulses, it agrees with the DRO. It's the DRO that's lost position compared to the program that generated it.
I've slowed the F1000 down to F400 and that seems to resolve the problem. This looks like an issue to do with the rate at which the DRO is capable of keeping up with the program. Maybe there's someone I could send these files and my setup file, I'm sure it would reproduce without a machine connected, after all, it's a dumb open loop system?
I'm using an ESS by the way.
This has nothing to do with the computer doing other functions. It does this regardless of whether the computer is standing idle or not. I thought the whole point of the ESS was to offload the work done by Windows. I've been happily surfing the internet, creating other 3D jobs and all kinds of things while another job has been running without a hiccup.
I'll switch back to the aqua screen since that doesn't affect anything. It's an awful lot better than the default one which is a nightmare in my opinion. I do wish things like the Home buttons weren't dangerously close to the Zero on the DRO's that's an accident waiting to happen.