Wow! So many replies from the gurus 🙂
The app was running in the background while I've been playing with several other applications - AppStore, Safari, Mail.
I don't remember if I run camera app.
Then get back to the app in 10 - 30 minutes and saw the lost context error.
I agree, the cause could be the low memory notification.
There is one native extension in our app.
A custom made iOS Settings UI.
This is how UI ViewController is being added to AIR view on native side.
id delegate = [[UIApplication sharedApplication] delegate];
UIWindow *window = [delegate window];
[window.rootViewController presentViewController:myOptionsViewController animated:YES completion:nil];
Probably native UI extension is an unexpected (unsupported) case.
I've been trying to repeat the error once again, but didn't succeed so far.