I will try lowering the rates, the last run I did at 25mm/s would it need to be much slower, how about 15mm/s?

I've not checked for backlash simply because I'm not entirely sure what it is, but would backlash cause this type of fault? The machine seems to run much better than before(I have changed the BOB and some optocouplers) and the Z axis fault it had before hand has also gone, but now I have this.

I'll get there in the end. :)