This isn't really on the same topic, but most French reporters think it is.
RATP are going to replace 30 escalators (along Metro lines 14, 6, and 13) that are less than 10 years old, at a cost of ^6M minimum. They are suing the makers (CNIM), citing design faults which have led very high levels of failure, maintenance, and their being out of service.
The thing that the press have been having fun with (
e.g. Le Figaro) is that they are "too wide". They were procured as having treads 1 m wide, instead of the customary 0.9 m, but I am sure the tracks were built to this width too. I can only imagine (as no-one has bothered to report on it) that squeezing the running gear into the narrower space involved some design compromises that just didn't come off.
RATP have explained the wider treads were meant to increase throughput. Really? How? I can't see how you can get more people side by side. It makes more sense to me it was to cope with luggage on wheels which, even if not so big as to be dangerous (and justify "please use the lift" signs) does get in the way.
RATP has already sued CNIM (and won, at least partly) over a moving walkway at Montparnasse, installed in 2002 and which never worked. That might explain why I found it such a long walk - if you think some of the treks in London are long, try Montparnasse to Montparnasse-Bienven^e Metro.