Plug-hole woes

[Steve Maskery]

Morning chaps
A couple of days ago I cleaned my bathroom sink. I unscrewed the plug to get at the drain, screwed it back again and all was well. I've done this many times

However, yesterday I came to use it and it was not sitting properly. It should stand upright, whether or not the sink is plugged. Push down to seal, push down again to release, a bit like a ball-point pen.

It won't go down properly, if I do manage to get it down it either pops up of its own accord or it has to be prised up. Nothing that I can see is obviously broken or missing. Does anyone know how this should go together? It doesn't look like I have many options!

Any help gratefully received.

I'm out for the afternoon, so if I don't reply, I'm not being ungrateful

 

[NazNomad]

Not sure if it's the same, but ...

... has your circlip come adrift and is sitting in the waste trap?

 

[Steve Maskery]

Thanks for that Naz.
The answer is I Don't Know, but I'll investigate. Of course, the trap is difficult to get at, as it is inside the pedestal, not underneath in a cupboard.