Intermittent faults can be a nightmare to resolve if there isn't a detailed datalog of the event; it's a bit like noticing the cookies have all gone (as usual) but the kids deny all knowledge: unless you catch the little ******s in the act, there's only surmisation and maybe a bit of circumstantial. The window-drop happened in our car a few times not long after we took delivery - but hasn't occurred for the last three months: I have a sneaky suspicion it was related to water ingress to the switches, following a car-wash dim moment on the owner/operator's part... So this might seem stupid, but perhaps the tights full of cat litter/rice might sort it (if placed in close proximity to the door switch cluster, rather than being worn, obs).