On Thu, 20 Jun 2019 22:59:25 +0100, Charlie Pridham
wrote:

The quality of clips seems to vary from supplier to supplier with some
being more fierce than others and I too have come across clips that are
so loose they are hardly worth having and the first bit of wind will pop
the glass out.

Try a small quantity of clips from a different source just to see if
thats the problem

I bought stainless clips because I wanted them to last but I am going
to buy some galvanised ones from a different supplier to see if they
are a better fit. I've used galvanised clips when I built the same
greenhouse at my other houses, so I'm sure it's not user error of me
not knowing how to fit them!