Is there a way to keep your app icons sorted by name in LaunchPad?
This is a known bug and has been filed with Apple. All we can do is wait on a fix. 

The database gets corrupted when a new entry is added and moved. 

The only current workaround is to delete the database and start over, but bear in mind that once a new item is added and moved to a different position, the corruption will occur again. 

The database is located in ~/Library/Application Support/Dock