When I first read the OP's post I did not recognise the "the little spring catch that links mesh to blind proper" .
Now I am beginning to realise that it is likely the (grey coloured on mine) plastic retainer that has "REMIS" embossed into the face.
Actually, one of mine became detached a couple of weeks ago, Mrs Anseo had been 'pulling' the blinds apart, not realising that a
very gentle finger depress of the catch releases the lock.
If the plastic lugs on the catch are not broken then the catch should not come adrift or require any adhesives to secure it in place.
Anyway, a simple push fit to relocate and secure the item, I think they work rather well and should give long service.
Like a lot of things on caravans, if something does not operate easily it may be the case that we simply do not know the correct method of operation, as I find out all too frequently
.