If you use the iOS app, and you still get that "occasionally the screen goes white/grey/black when returning to the app", I have a beta version of renshuu that will hopefully fix it.
In order to join, you'll need Apple's "TestFlight" app, which is used for test versions of apps. After that, go here: https://testflight.apple.com/j...
Normal usage is all that is needed to test this. Please report issues HERE, and not through TestFlight's reporting mechanism.
That sounds like the fix then. For the technically-inclined: what was happening (as expected) is that external factors in iOS was forcing that part of renshuu's app to leave memory. The fix is able to capture that event (but cannot prevent it), and say "when this happens, automatically reload the current page."
