Hi all.
We are fixing up a plasma cutter with a refurbished Win7 PC Dell Optiplex 780 with parallel port operation.
During final stages of installation and testing, a problem was encountered:

Whilst jogging any of the three axes, despite a continuous button press, the machine intermittently stops and starts moving.

interestingly, Both the DRO and the axes display zero movement during these stops.
This tells me the issue is unrelated to the parallel port itself. Though I'm not betting on it just yet.

The stops indicate no apparent pattern and manifest completely randomly, sometimes not manifesting at all for up to a minute or so.

Conditions:
-Issue occurs at all Kernel speeds
-Win7 32bit parallel port config
-symptoms affect all axes similarly.
-Employer owns valid Mach 3 license
-THC is Proma150, taken from the same machine before old PC controller failure. Working fine with G31 post processor.
-No error messages or warnings to be found.
-There are no other problems to be found.
-all assigned inputs and outputs aside from motor outputs are working properly.
-all stepper/driver pairs have been tested using an arduino Accelstepper test board prior to installation.
-Z-axis is noted to produce a different tone depending on direction of travel, though all three axes display the intermittent stopping issue.
- All axes stutter at the same time as eachother, ie, the whole machine stutters
-Stuttering duration varies from non-existent, to pausing for several seconds or even indefinitely until the button is released and pressed again. seemingly randomly.
- problem persists irrespective of active-low/active-high stepper output configuration.

I am unable at present to test whether the issue occurs during NC operation or only in jog, Will be working on that and then updating the thread.

Kind thanks in advance for any assistance provided.