Hi, it seems to me that the fullcalendar view has its own feed caching separate from ics calendar. Ie. turning off caching, reloading the feed on page reload or loading via ajax does not changes to edited events.
FullCalendar does not have any kind of caching. I think I may need to see your System Report to help troubleshoot this issue. Could you please submit the support request form including your System Report details? Thanks.