If your case is:
- "Start in" smart folder
- Two panel layout
then please update to latest 1.12-dev (the "development builds") section.
If not please check the setting mentioned by mike and also note that:
By an Android convention, only Back "closes" an app. Using Home is supposed to preserve an app's state when it's restarted.
In other words, accounts will not expand (but will stay as they were) if you use Home. Please use Back so the subsequent "restart" really is that, and the app applies its "which accounts to expand" logic.