Agent Workspace - OOB add/remove actions do not work in "Incidents by same caller" related list defined by sys_relationship record.
1. Navigate to Agent workspace.
2. Open incident list.
3. Open any incident record.
4. In the form section under the related lists open Incidents by same caller.
5. Check that the UI Actions Add and Remove are present.
6. Click on Add and select incidents, these will not get added.
7. Check incidents to remove, these will not be removed.
This problem has no workaround, is under review and targeted to be fixed in a future release. To receive notifications when more information becomes available, subscribe to this Known Error article by clicking the Subscribe button at the top right of this form.