This might work for most users. Open you waze and choose your destination.
After everything is set, turn your volume to the max or to a level you can clearly hear the directions. You can also choose voice navigation with street names (available in some countries) in the voice navigation options screen to help you get better voice directions.
After that, If waze is working and navigating you to where you need excllent. if not, just press the home button, it will take you out of the waze screen but waze will still operate in background.
Wait for a few minutes and VIOLA Waze will work flawlessly as long as it doesn't show on the screen. if you enter to the app to see the map, most likely it will lose gps signal again. But after you'll be out of the screen gain, even if the screen shut down, it will work well. Right now this is my favorite fix option.