So I just got one new CNC Mach3 USB controller and 4 new drivers.  I got the DM542 drivers because my old once where making the stepper really noisy.  Anyway on to the weird thing.  If run a G-code like G0x100.  The x moves across to 100mm but the weird thing is sometimes another counter in Mach3 like Y or Z registers either 0.0050mm or -0.0050mm.  But the z/Y never moves.  Also when I say G0x0 the x goes back to 0 but it usually also registers 0.0050 or -0.0050. If I then say the command again to G0x0, nothing happens.

Any ideas

just adding another comment.  I just tried this again with only the usb cnc card on.  The motors and drivers were not on.

It did the same thing.  really wierd

It's not really that weird.

With your 'steps per unit' setup 0.0050 is your step size and Mach3 will not attempt to make a movement which is smaller than your step size. Essentially 0.0000 and <0.0050 is the same dimension as far as your machine is concerned and that is the way Mach3 is interpreting it.

Tweakie.

I understand.  But how does running the command g0x100 cause a different axis to say its moved .0050. 

I don't know the answer to that one 
Perhaps it's one of the mysteries of Mach3 

Tweakie.

The problem is .0050 is exactly one step on my machine.  So if it makes that mistake a bunch of time my part will be ruined.  I put a ticket in with them.   

The 0.0050 is not really an error (although it appears to be) and it will not be cumulative so you have no worries about your parts being spoiled.

I would be interested to hear what the support team have to say about the issue so please report back when you have an answer.

Tweakie.

After a little more testing this morning, I decided to tell the settings inside mach3 that I was using 1/16 steps vs 1/8 steps.  An lo and behold now when I run the machine it moves the same axis weird by 0.0025 vs 0.0050.  There must be a bug in Mach3

There must be a bug in Mach3