X240/X250 curious Fn-key behavior

[RealBlackStuff]

I have an X240 with backlit LiteOn keyboard, where the Fn-key sometimes behaves strangely.
They key-mechanism is also different from 'normal' keys, see this:
Click here for a bigger picture

Rather unusual is the metal clamp that goes from the key cap through two openings L and R of the key mechanism.
Does anybody know why that clamp is here, and/or what it does?

Sometimes the Fn-key functions correctly, including switching on/off the KB backlight via Fn-spacebar.
Other times it does nothing.
I can't see any dirt or broken/missing parts, can you?

This behavior is apparently not uncommon with the X240 and has been a thorn in people's eye for many years.
This Fn-malfunctioning can happen from buying new, from swapping the keyboard, but most likely (I guess), from updating the BIOS.
And of course, since UEFI you no longer can revert to older BIOS-versions, unless you go through great hoops!
As usual, Lenono doesn't give a hoot and has never tried to rectify this!

Does anybody have any explanation why this might happen?

[Thinkpad4by3]

Well for the metal bar it looks like a key stabilizer, but it would make no sense on a 1 unit key. Mechanism also looks clean. Did you try leaving the keycap off for a few days and seeing if the same problem results just by pressing the dome on the off chance the keyboard isn't pressing the dome right? I'm also wondering if because it is a lit keycap, does the metal bar act as some sort of wire, not a stabilizer, and in that case try deoxit on the wire and the contacts in the keyboard. Unlikely, but worth a shot.