I too had a new windscreen fitted late in December 2016 and noticed the rain sensor wasn't fully pressed against the glass (had a kinda air bubble trapped) the screen fitter was in a foul mood and I'd already snagged the scuttle plate he'd left standing proud of the glass....thought it best not to say anything so went back inside with my cup of tea and slippers
The sensor still works fine really but not as good as it could be, takes a few adjustments on the 'wheel' to find a suitable setting. TBF though I never thought it was that good anyway, an 'adjustable' auto sensor? what's that all about?