Those do fail, generally you find the plastic goes brown, breaks and drops the wire out, along with a lot of powdered plastic and a small metal spring tab and the thinnest brass ( or plated steel) you can get. You use a paperclip, straightened out and used to press the spring back by gently pushing in the slot next to the wire then pulling back. Or just wriggle the wire till it pops out.
I generally find that the whole fitting with tubes is cheaper than the 2 end fittings as spares, unless you are willing to buy a box of 100 of the end units. Of course the cheap Chinese lamps fail before the fixture, or the even poorer electronic ballast dies, and then I simply put in the 2 magnetic ballasts ( they rarely fail, most commonly the spring connector on them does the dirty disintegrate, but then you use a 2 way screw terminal to replace it) and the 2 starters then it lives for another few years.