His rails look exactly the same as mine (before I paint them). I don't mean the damage - I haven't ever had damage like that, because I am very careful with them until the rail is painted.
I love Maise nucs, and have 15 or so, but at the end of the day that rail is a thin strip of polystyrene (and not particularly high density polystyrene either) and as such it is inherently a weak point - the best design in the world can't get round that. Cleary Swn58 has given one of them a bit of a knock/squeeze, but that can happen.
I think a phone call to STBK will be met with "yes, we can confirm these are made of polystyrene - don't whack them or grab the thin bit with your thumb and squeeze it"
But who knows - if they are feeling generous he might get a free one out of it. Plainly if it came like that, that's a different matter, but I don't think it did?
(And as I say - painting the rail strengthens it significantly, as it removes the tendency for the little balls of poly to flake away from each other)