Thank you for making all this effort!
I tried the special build, but the lost file fragments keep appearing. The number increases with time (maybe with the number of shutdowns).
Could be related to the extra large 400GB Sandisk SD card I am using.
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The lost fragments start like this:
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Rb
Å–²ã #ø[ ë5 Ì› ade in duration: 0
crossfade fade out duration: 0
dithering enabled: on
compressor threshold: -9
===============
or like this:
===============
Rb
)~" ´PLʰþ¿ÄúÿH# Ì› g Amadeus Mozart.mp3
Sibelius Pieces/;75 - Sibelius - Finlandia - Andante sostenuto - Allegro moderato - Allegro.mp3
>3;9;71697;0;1638;0;0;10000;10000;/Books/
===============
Seems no data is actually being lost, so some enjoyment can still be had

Thanks again.