The Desktop Plugins provide the ability to set file locking preferences. The following preference results in files being locked when they are opened:
Always lock Connections files when opening and unlock when publishing changes.
While this may be the desired behavior for most interactions with files, it's possible that certain file types are typically only viewed (for example, PDF files), and thus there is no need to lock. If you view a PDF file in this scenario, it will get locked, and you have to manually unlock each time you finish viewing.
As an alternative, it would be helpful to extend "Always lock" option to have a list of exclusions (so that automatic locking still occurs for all non-listed file types), or to have an option to only automatically lock specific file types.