If the inbox is loading, you can swipe to open the left nav. After the inbox loads that action just dismisses your inbox, so it does not have the same effect.
After the left nav shows up while the inbox is loading, the subscribed feed either
- reloads in a couple of seconds
- doesn't load at all like this
I think this is a bug. Probably should not be able to open left nav when inbox is loading, no?