[itsme]

I used "Swap File" to replace HLJPA-028 - Big Band Era.pdf with the same file as before and retried backup & restore - same result.
d:\_MSP\HerbertsGoogleDrive\_MobileSheets\HLJPA\HLJPA-028 - Big Band Era\HLJPA-028 - Big Band Era.pdf
was restored to 
/storage/emulated/0/_MSP/HLJPA-028 - Big Band Era.pdf
(instead of /storage/emulated/0/_MSP/HerbertsGoogleDrive/_MobileSheets/HLJPA/HLJPA-028 - Big Band Era.pdf as expected)
I noticed that the audio files that it had attached were restored correctly, 
d:\_MSP\HerbertsGoogleDrive\_MobileSheets\HLJPA\HLJPA-028 - Big Band Era\Audio\Christopher Columbus (backing) Bb.mp3
was restored to
/storage/emulated/0/_MSP/HerbertsGoogleDrive/_MobileSheets/HLJPA/HLJPA-028 - Big Band Era/Audio/Christopher Columbus (backing) Bb.mp3
as expected.