Unable to switch to release build variant for Mobile SDK samples in Android Studio

The name already pretty much sums it up,

out of the box, I can open, build and run the samples in the Mobile SDK in Android Studio, but only ever in Debug mode. Bringing up the window for Build Variants, I can try to select the Release build variant, but after the task with output "> Configure project :VrSamples:VrCubeWorld_SurfaceView:Projects:Android", it immediately switches back to debug. From within the respective directories, I can run "build.bat" just fine and I can also switch to Release without problem on my own, custom-made projects. Any ideas what's wrong / can someone corroborate? I btw think I tried everything suggested for "can't switch build variants" (invalidate the cache, restart, delete .idea folder, doesn't help, the problem occurs on a freshly opened project).

I have to mention that I'm new to both Android and Gradle. In general, I would guess the Gradle job somehow fails internally and Android Studio reverts the selection, but the output I am getting is not at all verbose. For any hints on what I could do to get more info and discover the error myself, I would be glad as well!

Thx!