The Event Details metadata has optional and non-optional fields. The "duration" and "created" fields cause NullPointer exception if they are made optional in the org.opencastproject.ui.metadata.CatalogUIAdapterFactory-episode-common.cfg file. But there is reason that they should be optionally optional.
The motivation for making "duration" optional within the Event Details Metadata UI is that it causes confusion by showing a longer duration that the trimmed media and shorter time (i.e. zero) than uploaded media. The event details metadata duration field is originally set by the original event scheduled duration and is not accurate when the scheduled time has changed, and is not relevant if the event is trimmed or uploaded. The most accurate post ingested media duration can be found in the event assets media details UI.
The motivation for making "created" optional within the Event Details Metadata UI is that it causes confusion with the (unrelated, but similarly named) Event DublinCore catalog created field and the event and media package start time. Changes in the "created" event details metadata field does not affect other services or catalog. That field is only used for display in the Admin UI.