ICalToJSON page 'duplicates' modified recurrent events

When editing a recurrent event instance in google calendar and then importing it into XWiki (through iCal link), the previous (unmodified) instance of the event is still present, which manifests in duplicate events with different start/end dates in the JSON and UI.

Below is an example: the @Home event (second one with the id `...@google.com_2`) was moved from 13:00+0GMT (first picture) to 11:00+0GMT (second picture). In google calendar, the second event replaces the first one, resulting in a single @Home event being shown in the UI. In XWiki, both events are visible.