Steps to reproduce:
1. Create exactly one series
2. Add an event
3. Switch to Events Table
4. Reload page (to ensure the series created in step 1 is visible to the Event Details modal)
5. Open the Opencast log (assuming a all-in-one)
6. Open the Event Details modal
In the log file, you can see that a new snapshot is taken. In the Admin UI, a green arrow indicates that the metadata field "series" has changed (although no series is selected)
Should not create a snapshot obviously
Workaround (if any):
This is causes by the pre-select-from directive that is used in the drop downs and is supposed to select the option in case only exactly one option is available.
In the case of metadata fields, the use of this directive doesn't seem appropriate, so I have simply removed it which resolves the problem.