I have found that the issue as far as i can tell
appears when paving a road that has not yet made it to the client (and therefore seems to not exist) but actually does exist in WME.
I have also heard reinstalling works - but on a Android device there is also the option to simply clear Waze's application cache. From the Phones (not Wazes) "homescreen" go to application mangement (tap Menu, Manage Apps i believe - my UI is in Danish
), find the Waze app, Tap the Clear Cache button. That worked for me.
The next time you start Waze it will initialize like on the first use and of you will need to enter your username and password to log in again plus reset any options from default values.
This method is simply quicker and saves you having to find Waze again in the store and possibly download over a slow connection that you may even be paying to use.
Sorry to say I have no clue if iPhones have a similar option.
PS May I suggest waiting a while after the last drive (exit and restart Waze), especially if the last drive was done in bad network conditions, before performing the action - just to make sure that any locally stored data has been sent to the Waze servers...