Help! Stepper motors work with test code but not with controller dial

I'm in the process of building a reprap-based cartesian machine.
The setup uses marlin 1.1.9.1 on Arduino Mega 2560 + Ramps 1.4.
I am doing control testing with a ReprapDiscount Full Graphic Display + controller knob

It has the following stepper + driver combination

X axis : Nema 23(STP-59D5005. 3A ) + fysetc S109(marked as A4988 in my marlin build, manufacture claims it is a drop-in replacement for A4988)
Y & Z axis : Nema 17(1.68A ) + DRV8825
Extruder 1 & 2 : Nema 17(1.2A ) + DRV8825

It compiles well and the move axis command works with the extruder motors.
But when I try to do the move axis command on XYZ, the motors try to do something but doesn't quite get through.

To be a bit more specific, the X motor clicks each time I increment or decrement the move axis dial(it doesn't do this when I turn the dial back down below 0)
The Y motor just keeps on humming forever once I try to move it, and hums more intensely at irregular intervals.
The Z motor clicks once when I try to increment it and is silent afterwards.

When I run the below test code I found on this forum all the motors run happily.
Reprap test code

The wiring continuity is fine, and all the jumpers are in place.
If anyone has a suggestion on what I should be checking it would be very much appreciated

Edited 1 time(s). Last edit at 11/07/2021 05:56PM by Bottlejean.