I have just discovered a possible bug and a workaround which might help anyone else having this problem (Did a quick search but couldn't find any mention of this problem)...

I stored some music on my Tonido Plug and could access all the folders on my iPad but a couple of the folders were showing as empty on the iPad. On the drive (a USB thumb drive attached to my Plug), the files were showing present.

The problem was that the folder names in question contained ampersands. I simply renamed the folder names on my Tonido drive to replace the ampersand with the word 'and' and hey presto, the contents then magically appeared present when I opened up the folders again on the iPad.

Yes, we are aware of this issue. Thanks for reporting and your workaround. We plan to fix this shortly.