Saving failes when relative pathnames used on command line
Starting MuseScore like 'musescore path/to/file.mscx' makes it fail to save; an strace shows it tries to access 'path/to/path/to/file.mscx' intermittently. Starting it with the full path ('musescore /home/foo/path/to/file') succeeds.
lasconic suggested in IRC to resolve pathnames from the command line to their absolute paths early. (Just take care to not break symlinks.)