Agreed - you also have to ADJUST the order of the LOCAL FILE stuff.
I was getting some weird results as well. I used MP3TAG to update all the tad info in my files. Had to use the command in POWER SHELL - ATTRIB - S -H . /S /D to reset some attributes on hidden files in there…as the FOLDER.JPG file was marked as SYSTEM and HIDDEN - I think Windows Media Player did that at some point.
I made sure all my folder.jpg files were 500x500 (72dpi) and made the change here:
AND
to adjust the order to look for data… did. I then REMOVED the LIBRARY, did the PLEX DANCE ( The Plex Dance ™ )
RE-ADDED the Library – and magically 98% of them were correct. The ones which were wrong still - I re-checked the ID3 tags and fixed any errors and then RE-SCANNED LIBRARY - ouila!!! All good.
I have over 60,000 songs in my collection. Now if PLEX would just make COLLECTIONS work like the MOVES do. 
bh
