Time Master "stores" the calendar ID that Apple gives us. Hopefully they have not changed this and are no longer providing the ID. Are you using a built-in calendar (e.g. "Personal") or some linked calendar like Google?
We were seeing sort of the opposite thing where it was not publishing to the calendar at all. If you have multiple devices, make sure that only *one* of the devices publishes to the calendar, otherwise you will see all sorts of duplicates.