This only happens sometimes, but on occasion I'll save a file as a midi, ok? It sounded fine when played back IN Sibelius. Then, I go to play it as a separate midi after I've saved it, and at one point in a slow section, at the beginning of a measure that is so lovely and ppp, there's this strange little clappy sound, almost like someone dropping a cymbal in the back during a band concert

It was kind of funny at first...
However, now I'm annoyed because I can't figure out why it's happening., and I can't seem to get rid of it. I tried resaving it as a midi again, same problem. I tried deleting those measures and rewriting them with newly created bars in case I accidently slipped some sort of bizarre midi text in there instructing it to make that noise. No dice.
Is there anything I might try to fix this problem? Why is it happening?