Could be that you use different FETs than me or something like this. You could try to reduce the 470k resistor to shorten the time required for long press.
But I can also play with this once I got mine.
Multimeters often have 10M impedance (unless you got one of the better benchtop ones that got Gigaohms impedance in the lower ranges).
This hints that a permanent 10M pulldown could help to solve this. But also see my post in the other thread 7REV1+ ideas SPI ADC, IO expander, roadmap - #70 by electronic_eel