distorted notes

been using midi backing tracks for at least ten years and had this problem ocassionally. A note or two within the track will suddenly become distorted. Sounds like a note being stretched or maybe like a cat scream. There is usually a tie in the measure, but eliminating the tie doesen't seem to help. I usually end up re-downloading the track and scrapping out the track with the bad notes. The track didn't have the flaw before, so this is something that happens as the track gets used. I need your help!!