Hi,
I have a 3 axis version of the same driver board and after going through some nightmares I was about to order a more expensive board but I will try your workaround before.

While I am waiting for some 74HC14 I figured i would start cutting traces and getting ready.
See attached:
Click image for larger version.  Name: cheapbrd.jpg  Views: 15  Size: 105.4 KB  ID: 114150
A - I removed the 10k resistor coming from pin 3 of TB6560
B - I cut the trace and will use both sides to connect 74HC14/resistor connections
C - Coming from pin 4 of TB6560, my board appears to reflect your changes already so I just wanted to make sure you did not meant to change this around.

This is how my board is configured (too bad there is no version number):
From pin 4 of TB6560 going through 1k resistor then going to pin 3 (emitter) of PC817 and pin 4 (collector) of PC817 is going to +5V

Thanks

Mike