Events are displaying incorrect (technically repeated) titles in Week View only. Day View, List View, and Month View are working as expected.
In Week View the event titles are mostly showing as one other day’s event title. Depending on the week in question, the incorrect event title may change from one incorrect title to another.
On mouseover, the hover window displays the accurate event information. In any other view besides week, the event title is displayed correctly.
Disabling all plugins had no effect, nor did reverting to the twenty seventeen theme.