They ae really hard to get apart.
You have to sort of tilt the white switch part side to side ( Only a little bit of tilt ) while pulling out at the same time.
Eventually, they WILL pop out of the threaded black socket part of the button.
The theads are on the outside ofthe black body and is really for the plastic nut to hold the button up against the metal deck.
The white switch part is held in not by threads, but by some sort of a "molded edge".
So you have to really pull hard as you tilt ( Not twist ) the white switch part to un-pop it out of there.
I hate to say it, but those buttons were somewhat of a bad design.
As they got older, the heat from the lamps, and aging, made the black plastics brittle.
If you get the white switch part out without breaking the black threaded part, you're lucky.