Jog Speed slider

comp.setprefix('mypin')

Do you have a pyvcp with your current axis config? That usually causes the halpins to be renamed pyvcp instead of axisui

I think Phil fixed this, but it might be in 2.9

Wish I could help, but I'm still on 2.8.2 with currently no test machine at hand to do any experiments. On that version the script works as expected.
The whole thing is highly dependent on axis.tcl and axis.py and kind of a 'hack', so any changes that might have happened from 2.8.2 to 2.8.4 can affect the script.

As already suggested, 'print-debugging' through stuff makes sense.