It might be more successful if you collect the RecID of the Employee in the request offering and then pass that to SR and in turn the Employee Record.
Assuming your "Name of Leaver' field is a drop down, in the settings you can collect additional fields in the RO:
Then you can add a new read only field on the form which you set to a default value (the RecID of the leaver):
You'd then make the field not visible. That might then work with your existing setup. If it doesn't I'd probably try using a Business Rule on the Service Request BO that triggers on change of your TargetUser field, that way you know the SR is saved before it tries doing the update.
Let me know if you have any other questions.
Thanks for the tip, helped enormously. I found I had 3 issues (OK errors).
1. I had used the display name - Changed this to RecId as advised (Cheers Ross)
2. Although I had added a unique link field just for the relationship I had for some reason selected the ParentLink - Changed this to the EmployeeRequestLink field I had added
3. Biggest issue, I was trying to use a compound quick action, this did not work. - Changed this to use a single action for the Search and Link, then another action to update the Employee fields
So here is the final config:
In the Employee Object I added fields
In the Service Request Object I added fields
In the Service Request Object created the relationship
In the Service Request Object I created quick actions
In the request set the workflow to
Where the update block put the employee RecId into the TargetUser field and the date entered onto the form in the Update_A field.
Hope this helps anyone else who comes across this or a similar issue.