Welcome aboard, megamoze.
This is a problem with the U-Trak wire colors that I thought Andy was going to fix several years ago.
Look closer at the wire colors in your photo.
Top is 1. red, 2. blue,
3. black,
4. purple.
Bottom is 1. red, 2. blue,
3. purple,
4. not used. (X-axis ground is jumpered to the Y-axis ground inside the U-Trak, so pin 4 is not used.)
For some reason, Andy used a different wire order for the spinner axis than he did for the trackball axes
and has U-Trak wires that don't use the same color wires as the mini-pac harness for connectors that go together.
The mini-pac harness uses green/yellow and orange/brown for trackball axes and blue/purple for the spinner axis.
The U-Trak has blue/purple wires for one axis.
Connect the mini-pac trackball connector with orange/brown wires to your U-Trak blue/purple connector, matching red (5v) to red so you don't short 5v to ground.
Scott