Richard Clay wrote:

Possible bodge solutions include aralditing or screwing the drifting piece
to the junction, perhaps? And why does it happen?

I would guess that it works its way out as it expands and contracts
with temperature. I've noticed that the longer lengths of our plastic
guttering 'tick' quite noticeably when the sun shines on them which
suggests they're expanding quite significantly.

I think I'd go for screws (or even some cable ties through holes) to
fix it.

--
Chris Green )