File and folder names in HFS Plus are also character encoded in UTF-16 and normalized to a form very nearly the same as Unicode Normalization Form D (NFD) (which means that precomposed characters like "å" are decomposed in the HFS+ filename and therefore count as two code units and UTF-16 implies that characters from outside the Basic Multilingual Plane also count as two code units in an HFS+ filename). HFS Plus permits filenames up to 255 UTF-16 code units in length.
Could it be that the files were created on a non MacOS system and it is having problems when MacOS HFS Plus normalization differs from standard NFD. Is it only occurring for some special characters ?
Could you try manually modifying the file to remove accents to see if Jaikoz can load files, and let it resave on MacOS so it adds the accents in a mac compilant way that allows to be loaded okay.
Sorry for the late answer, I did not see you had responded. They have not been saved outside the Mac ecosystem as such. But there was some sort of resetting of the WD disks on my QNAP external drive which may have upset formatting.
In any case you are on the right track. The albums that Jaikoz would not read I could also not open in the OS X Finder. A simple rename with the same special character solved that issue.
However, a second issue is that Jaikoz reports a large number of files as "not recognised as audio files, they may be corrupt". For these albums Jaikoz appears to attempt to open more files than there are on the album, e.g. 17 vs the 9 that are actually there. The "corrupt" files are listed with outdated filenames that I have updated manually, and the albums seem to get opened anyway with the correct number of files.
This problem should also be in the log file I sent you.