I've been testing some stuff regarding the NavDrawer and screen orientation lately. The app must have all orientations checked and also auto rotation.
Here are two bugs that I've found:
1. The Canvas resolution must be something like 360x640 (X < Y), but start the app on landscape (mobile - android). The GUI elements are larger than normal (I think the resolution doesn't adapt to 640x360), but switching to portrait, and back to landscape corrects it.
2. Open up NavDrawer on portrait (mobile)
Switch to landscape -> the dark area of the NavDrawer is smaller (it's not autoresizing when the orientation changes).
Using latest MaterialUI with Unity 5.4.1p1. These are minor bugs, so whenever you have some time, please take a look at them :)