... ah, but wait a minute, the following doesn't seem quite right. However, the back button isn't involved.
- Group by first letters is checked
- Open Group drawer - No Grouping
- Tap Authors - Authors expands to show the Authors A-Z subgroups.
- Tap A - opens A subgroup to show 4 A-authors
- Tap Authors again. Error message 'Something has gone wrong...' and the top level Authors line has disappeared, the 4 A-authors still shown.
- Need to tap top line Groups to reset everything.
Does this help or obfuscate further?