What we're dealing with is redundancy. Read the paragraph's opening sentence closely, slowly. Focus on what comes after the comma, but disregard the material between the dashes. We're left with:
... and sometimes the voters occasionally miss on top-five teams.
Sometimes means "from time to time." So does occasionally. The sentence needs only one of these synonymous adverbs, not both:
... and sometimes the voters miss on top-five teams.
... and the voters occasionally miss on top-five teams.
Once in a while, use sometimes. At times, use occasionally. Now and then, check your work to be sure you haven't used both.