Embedding unity into existing android app: UnityPlayer.quit kills app process

I successfully embedded my Unity scene in one of the activities of our existing Android app. It's not a top activity, so the back stack looks like: Main -> Some other activity -> Unity activity.

Now I want a user to return to "Some other activity" when they press Back button while in the Unity activity. However, UnityPlayer.quit actually sends -9 signal to the process after performing an engine shutdown. This kills the whole app.

What can I do to shutdown the engine without killing the process? Something like Application.Unload (which I didn't try yet because the docs say: "Only supported on iOS and Windows Store.")...

I'm aware of starting activities in different processes. But this has other negative implications...