Hi. Whilst driving this morning I switched on the windscreen wiper on my S reg Ford Fiesta and the driver's wiper stopped in a vertical position on the return cycle (the passenger wiper returned as normal). When I next switched the wipers on the driver's wiper flipped off the widnscreen! Does anyone know how I can solve this problem?

it could be wear in the splines of the spigot at the wiper arm base, there should be a nut at the bottomk of the arm which can be removed and the wiper arm pulled of the spigot,then inspect what condition the splines are in,with the wiper arm off operate the wipers and see if the spigot moves, if not the linkage could be damaged.