Momentary power switch + LED

[coldnpale]

Hi again,
So, after all I added a momentary switch according to https://github.com/recalbox/recalbox-os/wiki/Add-a-start-stop-button-to-your-recalbox-(EN).

I uncommented only:
system.power.switch=PIN56PUSH

The result was being able only to turn on the Pi with the switch. Turning it off doesn't work.
Also the LED was on for about 3 seconds after I turned the pi on, afterwards it was going off. I managed to keep the LED on with a solution I found in another thread (https://forum.recalbox.com/topic/11266/led-status-light/10)
by adding the line "enable_uart=1" in the config.txt

Any idea why my switch isn't working for pi shutdown?
(rpi3, recalbox 17.12.02)

[coldnpale]

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)