[Steinway]

I was just about to sit down and write a very grateful "Thank you" post for the new update, when disaster (ie, black page) struck again! But this time it was slightly different than before: The black page was now accompanied by an error message (either because it was actually a different issue, or because Android 4.4.2 gives more helpful information than Android 5 (remember, I recently downgraded). If this is indeed the same issue, it seems the problem may be something completely different than what we've hitherto believed.
Anyway, what happened was: I opened the song, turned a few pages, and suddenly got a black page with the message: "File not found: [Location such and such].pdf". I was too perplexed to note exactly what file path was mentioned, but as far as I could see, the file which could not be found was the file which I was already playing from, and which had already successfully displayed 4 or 5 pages. How strange! When I went back to the library screen and opened the same song again, everything was back to normal.
May this whole problem have something to do with wrong path names or duplicate files? How could MSP open and display the first pages of a file, and then complain that the file in question doesn't exist? I have actually noticed strange things happening to my path names lately, but wanting to get the black page issue fixed first, I haven't mentioned anything about it yet. But may these things perhaps be related?

I'll try to describe what I've experienced lately:

I have always kept the "Let msp manage my files" option unchecked, prefering to manage my own files. I have had the pdf files stored in a folder called "Noter" (ie, "Sheet music" in Norwegian) on the tablet itself, with subdirectories "Beethoven", "Mozart" and so on. I've also organized my audio files in a similar way, but on the external sd card.

During Easter vacation, desperately trying to get rid of the black page problem, I made a backup .msp file of my library (including settings, but not including audio files), uninstalled MSP and reinstalled. I didn't delete any files, but restored the library from the .msp file to get my library back the way it was (selecting to keep original folder layout). At first I noticed nothing special, but then, when I tried playing an associated audio file, nothing started playing. Examining this closer, I noticed that the path under the "Audio" tab had mysteriously changed after the backup - from "/storage/extSdCard/Musikk/Schubert/SchubertTrio1.mp3" to "/storage/emulated/0/Android/data/com.zubersoft.mobilesheetspro/files/SchubertTrio1.mp3". This path and file didn't exist, which explains why no file started playing. I had to manually edit the path (for this and all other audio files) back to the correct one.
What I didn't notice then, but have realized later, is that all the pdf files were probably also duplicated in the /storage/emulated/0---etc folder after the backup, ie as if MSP were set to organize my files (which it wasn't).

Only now, after downgrading and wiping all data from the tablet, did this became apparent to me, as my original folder "Noter" was almost empty after restoring my backup, and most of my files ended up in the /storage/emulated/0---etc folder. I still don't understand why, as I've always been very careful to uncheck every box asking if MSP should organize my files. Note also that it was almost empty, not completely. Some of the files still ended up in my own "Noter" folder (!)

Anyway, I guess something must have gone wrong during a backup, either now or sometime in the past, making MSP look for my files in two different locations at the same time (?), both mine and its own folder. Could this in any way explain what I'm experiencing, and the mysterious error message I received today? Maybe even the black pages I've seen in the past?