When editing JIRA issue dates, only start date is editable

Repro steps:

1. Add a JIRA Issue dates event.
2. Select Add start and end date...
3. Pick two custom date fields.
4. Edit an issue from the calendar.

You can only modify the the start date of the range. The end date of the range is grayed out and cannot be modified. When changing the start date, the end date is also inconsistently automatically modified.

As a workaround, you can modify the end date by doing Drag&Drop from the end of the box of the JIRA event.