The biggest thing you can do to make Step/Dir noise resistant is to make them differential. All my servo drives can accept single or differential so I make sure I take advantage of them being capable of differential by using it. Not saying thats your problem and not even sure if your drives can accept differential but its something to consider as it makes wiring less problematic. Hood
X should increase in value as you move from Left to Right, Y should increase in value as you move from you to away and Z should be Sero when fully up and move negative when going down. Can you attach your xml as it may make the issue easier to find. Hood
On my mill I have the Safe Z set in Machine coords and to 0mm so I always know exactly where the Z axis will go to, ie as high as possible above the table. Hood
I am not meaning to be unkind but the wiring is not the best and I see no shielding at all, I would hazard a guess that noise is at least part of your issue. Hood
I have seen it mentioned several times that double opto-isolation can cause issues and definitely recall some saying that when they connected direct to the port to test their issue was solved. I am not an electronics guy so I can only go with what I see people saying works for them.
Its a Holiday long weekend in the UK so possibly similar in other parts of Europe? I was looking at the cncdrives webshop earlier and they said the Dugongs were in stock, did you try direct from them or was it just via CNC4PC that you tried?