Did you try turning your phone off? Sounds to me like some other app has locked up the GPS chip. Usually firing up the Apple Maps app fixes that, but sometimes you gotta power off/on the whole unit to get it working properly again. It’s got nothing to do with the Waze app.
Is there a way to disable the landscape mode? I can’t find anything in options. The slot I sit my phone in while driving makes the landscape mode activate, and it becomes nearly useless to me as I can’t easily read the thing sideways when I glance down.
Buy a windshield mount? 
Lol noticed that when you take a corner quite fast it tumbles to landscape mode.
Haha, yep, I have made it a goal to get Waze into portrait mode (I usually use landscape) as much as possible :lol: