Originally I backed up my non-Pro library and added that to the Pro version via the Pro Companion. It showed the aforementioned message at the end of the transfer, so, although all the files looked present I tried again with a copy of the library installed on the SD card. It showed the same message at the end, again it all looks complete, same number of songs, no signs of corruption found.
Same thing happened on another device today from a backed up copy of the Pro version's library.
If attempting to view the backed up library in the Pro Companion, I get the message "Error opening backup file. Unable to view song data".
Edit: since writing that, it seems at least 1 pdf file is missing. Unfortunately the file manager apps I have don't give details on the number of files within a folder.
Same thing happened on another device today from a backed up copy of the Pro version's library.
If attempting to view the backed up library in the Pro Companion, I get the message "Error opening backup file. Unable to view song data".
Edit: since writing that, it seems at least 1 pdf file is missing. Unfortunately the file manager apps I have don't give details on the number of files within a folder.