Hi,
issues with xml exports (& imports into Serato, Traktor et al even moreso..) are often due to font/character formatting issues of the files it tries to parse. There's no bug in MB I know of in that regard - and I export xmls with 500+ playlists to Serato/Traktor/Rekordbox regularly (which has had no issues with since cleaning up filenames & metadata).
So I'd start looking around the file/playlist where it cut off and do a regex search for non-ascii / non-UTF-8 and/or -16 conform characters in filename and/or the metadata fields that the itunes xml queries. (The above suggestion or some steps can get a bit complex, depending if you have any background in programming/etc,. but maybe this puts you on the right track...).
Good luck!
c.