The method described on this page (https://github.com/recalbox/recalbox-os/wiki/Add-a-start-stop-button-to-your-recalbox-(EN)) has always worked up until this update. Is editing the Python scripts necessary? If so, is there a guide for this? Thanks again!

my wiring is as follows:
momentary switch pins 5-6
led positive pin 8 with resistor
led negative pin 6 (bridged with switch's pin)

Problem is resolved. I'm not exactly sure what happened, it just seemed to start working once I got back from the gym. I had another issue in which the recalbox would not correctly boot using the switch, but I fixed that by disabling safe mode.

Go figure.

@danlevrai

Found my problem.... Hardware wiring issue. Thanks