Changes to a single recurring appointment do not "capture"-they revert back
If I make a change to a single recurring appointment and select "this event only" it takes and syncs across my devices. Then sometime later that single change is "erased" as if I never did it, again across all my devices.
It is as if there is some sort of "sweep" with iCloud that changes it back.
This link has more users with the same problem but different details:
It doesn't seem to matter if I make the change on my MBA, iMac or iPhone.