Stepper motors keep starting and stopping

[JAZZCNC]

i was looking threw some set up videos on youtube and it was showing how to test the driver with mach3, my test showed that mine was pulsing to slow. but when i tried to up the kh it never changed. could this be a slow computer problem?

Not so much slow computer but low voltage parallel port. It's common cause of problems on newer PC's and is most likely your problem if none of the other things I suggested have worked.

The easist/cheapist fix is to use PCI PP card but this can have problems because to all cards work with mach3.
Next option and by far the best is to get way from it and use external motion control card. This option is expensive thou.

Then you have the Drives.?? They are TB based drives and very very delicate things when it comes to voltage so don't what ever you do run them more than 36V or you'll fry them. 24V is safer but this does affect performance you'll get from the motors.

In all honesty they are Rubbish and not something I'd recommend building a machine based on but now you have them.!! . . . Well use them until they die.!
Trying to do CNC on the cheap 99.9% of time costs more than buying decent stuff and with a lot more hair pulling so not worth it.

There is another option you could try and is free and that is using Linux CNC. It may well work better with your PP than Mach3's driver does and end up costing you nothing.
I'm not Linux user so I can't help much on where or how but sure there will be others that can point you in wright direction.