Events disappear due to deduplication of events

Spotted with version 6.0.3 (elementary Updates).

Test scenario:

1. I create a one-hour event on the same day, called Test1.
2. I duplicate this event, call it Test2 and schedule it for the following day.
3. (a) If I now duplicate Test2, call it Test3 and put it on the day after next, the first event Test1 disappears from the calendar.
(b. If I duplicate Test1 for the second time at this point in the scenario and do everything else as described in 3a, the event Test2 suddenly disappears from the calendar.

This can be continued by the way, Test4 will remove other events created before.

I have tested both changing the time and using the same time as the initial event for the duplicated events.

I would expect any events I create in the calendar as a result of this scenario to be able to be saved and displayed.