There is a FB page called Self Build and Renovations Ireland, only a few days ago there was a discussion about this sort of thing, comes up fairly regularly, worth joining and doing a search to see what the solutions if any have been.
PS Search 'shattered window', certain companies seem to be worse for aftersale service too! One name crops up regularly, ironically I got all my windows from them 30 yrs ago and more again for extensions 15yrs and 1 yr ago, I've never had a problem with them.