Does anyone (Nym?) know if they just changed the spec of the button - i.e. metal to plastic, or whether they're a cheaper option - perhaps by only a few pence - that hasn't really paid off?
I'll see if I can find a copy of the old EAO Type 56 catalog when I get back into the rolling stock office next week, that is what is fitted to parts of the stock that I've worked on.
EAO are likely to have significantly changed the design from type 56 to type 57 though, assuming they are the EAO buttons and Bombardier haven't moved to another manufacturer.
We have some of the newer types kicking around at my company, but not the passenger operated types, mainly the 22mm ones, but housed in a sealed switch panel that is interchangeable, as mods are still going on, they haven't failed yet, but they haven't reached life expiry either.
I did work on some of the older EAO buttons, industrial modular ones that are very much out of manufacture, due to reliability issues on one of the fleets I was looking into a campaign service and/or replacement. The push buttons are up to a lifespan of around 10,000,000 operations now at a minimum and the contractors (switches) are living between 500,000 and 2,000,000 operations. I doubt that those BT are using have lived that long.
Everything I have used, the moving parts that bend in any way, or provide retention have been steel, or rarely in the case of push buttons there is a molded plastic spring. I rarely see plastic in things I put out for use on the trains, and even when it is, it's usually solid plastic with steel spring.