Some events like meetings where you are an attendee and not the meeting organizer cannot be changed – meaning they are not editable: You cannot delete them, you cannot edit them.

For example with an iOS event this can happen because there is no property that tells Pocket Informant that you are not allowed to delete/edit and when the edit/deletion occurs we don't even get an error from the OS for doing so.

If the event is synced with Google - same thing except we allow the delete/edit on our side, but then when you sync it gets overwritten.