Calendar Dismisses Events on its own

[dwayne1521]

This is a Sprint Galaxy S6. I had an update on Saturday night. Since then, any event that I have created in my calendar will notify me as usual but rather than waiting until I dismiss the event on my own the phone will clear the event on its own. Sometimes after 5 minutes. Sometimes after an hour. I've looked all through settings but don't see anything. Any suggestions?