[Zubersoft]

So the reason for this is because MobileSheets first converts the Windows path to an Android one, and then if it detects that the relative path starts with <song title>/file.pdf but "Create Subdirectory per Song" is disabled (which it is by default), it then eliminates the directory. This is to solve a problem where one device might have had that setting on but the other device does not, so MobileSheets has to figure out how to fix the paths to remove the unnecessary directories. This is also true if you change the setting and then restore the backup to get rid of subdirectories (which is a feature I recommend to users that want to get rid of all the subdirectories that were created in the past). 

So in your backup, the path is 557 Standards/557 Standards.pdf, which is exactly the path MobileSheets would have used if "Create Subdirectory per Song" was used, so it removes that directory as "Create Subdirectory per Song" is disabled in the backup file settings. If you use directory names not tied to the song title, then you won't run into that issue.

Mike