I am seeing the following in the tooltip that appears next to “Recurring Event”. It appears that there is a sprintf expression that isn’t being evaluated.
We’ve largely built our own theme. This markup is spit out by tribe_event_event_schedule_details called with all three parameters. (The documentation of that function could also use some work.)
Are you following the Themer’s Guide or using a hook to make your customization to the tooltip? Could you please provide your full code, file location, and filename?