So, it turned out that CV distance >0 and consecutive motions along the same axis (see code below) cause the machine to "thud" (at least in my case).
As for some routines I would like to still be able to set the CV dist >0, is there a way to set it through gcode?

i.e.:
...
G64 D0 // set dist = 0
G01 X100
G01 X200
G01 X300
...
G64 D1.5 // set dist = 1.5
...

Does anything similar exist in Mach3?

Pietro