I haven't completely figured it out yet, but I believe the problem has to do with the way sort deals with blanks. I need to go back and reread that part of the info page a couple of more times. Anyway, this combination works for me:
sort -k 2b,2b -k 3b,3r <filename>
Try it on your system and see what you get.
BTW, according to the info pages at `info coreutils sort`, the "+1 -2" stuff is deprecated:
" On older systems, `sort' supports an obsolete origin-zero syntax
`+POS1 [-POS2]' for specifying sort keys. POSIX 1003.1-2001 (*note
does not allow this; use `-k' instead."