I have three events published on the back-end but each event is showing twice on the front-end. These events were created from the "copy event" function on the back-end. I created a brand new test event and it is also showing up twice.
I am having the same problem after updating to 2.8.6c from 2.8.5b. Everything was fine before the update. Now I can't change the category on existing events and if I make a new event and pick a category it disappears.