Starting multiple Unity instances/tasks from same (android) application?

I am trying to run multiple unity engines in the same 'app', but in different tasks. By adding a new activity to the androidmanifest.xml I can create new intent that can be launched along with the main activity. This seems to work all right. The problem I am having is that, every time I start both activities and use Android taskmanager to switch between them, the one that I resume, crashes.

Just wondering if there is a some generic limitation on Unity side for doing this. For testing, both activities are starting same scene, but other is using it's own extended UnityPlayerActivity. Would love to get some pointers if somebody has experience with this. Ultimately I would be running two different scenes in different tasks. User could switch between them by using OS task manager.