When fingerprinting files that have long paths/paths longer than 259 characters, `fpcalc` seems to fails to fingerprint with an error similar to the following:

D: 01:08:15,355 acoustid\__init__._run_next_task:252: Starting fingerprint calculator 'C:\\Program Files\\MusicBrainz Picard\\fpcalc.exe' '\\\\BenjiQNAP\\Media\\Music\\Vaughan Williams, R․; Johnson, G․, Royal Scottish National Orchestra,\\Folk Songs of the Four Seasons Suite ⁄ Bucolic Suite ⁄ Dark Pastoral  [CD - CDLX 7289]\\06 Bucolic Suite∶ I․ Allegro.flac'
E: 01:08:15,355 acoustid\__init__._on_fpcalc_finished:209: Fingerprint calculator failed exit code = 2, exit status = 0, error = Unknown error

This happens even if Picard itself has no issues reading/writing the file, and regardless of whether Picard has the "truncate path to 259 characters" option enabled or not.

It seems like the `fpcalc` invocation above double-escapes path separators, which means even if you do enable the Picard "truncate path to 259 characters" option, the path `fpcalc` is resolving is actually slightly over that limit due to the extra escaping, and it will fail.