There's absolutely no way to enter any kind of postcode in my Z, so not sure what you mean by enter the first 4 characters of the postcode, that doesn't make sense as the only option is to enter the full street name.
Yes my Qashqai (or Q as I call it - ha ha) is only 1 year old, my Z is 3 years old. Have been living with Z-sat-nav-rage for a year now and finally decided to find a forum to ask about it to see if I was just missing something obvious....