That's a common problem with midis processed by Noteworthy; the program doesn't seem to do it very well. Its default length appears to be 100 rather than the 120 used by most other programs, so the midis often display full of unwanted rests. Doubtless other people will know how to get around that (viewing a midi generated in Noteworthy in another program, you generally have to reduce the resolution until the notes appear correctly) - personally, I gave up on it and use other software that does the job better.