Soldato
this is a very common problem on the 6N and 6N2, I have had both these models and the 6N one completely stopped working and the 6N2 was acting weird by the time I sold it.
Polos have always had crappy rear wipers!!!
my old 86C wago's never wanted to budge, and every other owners says the same, I just loved the 2KG weight advantage by binning the rear 'ballast'