In the meantime, I would remind the people who would like to experience a vintage keyboard to take a look at the Unicomp model M keyboards. They are not Model Fs or beam spring, but are rock solid, reliable, and sensibly priced considering their quality.
My Endura Pro started having issues three months in after arriving to me in 2013; I remember how it was $99 and shipping was $98, and then I had to pay VAT on it. It died quite quickly after and become parts donor for old IBM Model Ms I bought out from people’s attics. It was a wonderfully repair-unfriendly thing, too.
This was the same time, around 2013, so I like to hope things have improved since then. I know they did switch the controllers they use in the intervening years and they also replaced the original IBM tooling for the other parts of the keyboard, so hopefully things are in better shape now.