Number not displayed for incoming calls in sony xperia z1
If you have chose before upgrade to sync your contacts with google account, you can have this kind of problem. My advice is to turn off sync from google account (in Settings/Accounts), delete your google account from device (reboot, just in case), add again you google account and mark sync options as "on" in Settings/Accounts. It can take a while for contacts to sync back, but this was the way I escaped a touble like yours.