Xsue,
A friend of mine bought Dansk windows. All came with a protective plastic coating( on the glass only I think). They are very nice windows, however she has a lot of patio doors and these seem to be too heavy for the mechanism. She is moving in, in a few weeks. These may have been broken due to abuse from tradesmen, wheelbarrows etc etc, a lot of issues with patio's not closing properly. However I think all windows/doors will have initial issues, due to abuse, mortor sand etc etc in grooves and hinges etc etc.
I am in the process of ordering from Rationel and they do NOT coat the glass or frame. I will have to do myself.
I do not know oif they provide this service or not.
So your issue is not a once off as far as i know.
Bear with the teething issues, they will work out. One issue is that the installlers do not work for Dansk, so any issues will be difficult to pin point to Dansk or installers.