How To Fix WL383 - Illegal expression '&' for agent

SAP Error Message - Details

• Message type: E = Error

• Message class: WL - Workflow: run-time messages

• Message number: 383

• Message text: Illegal expression '&' for agent

What causes this issue?

Expression &V1& should provide a responsible agent for workflow step
number &V2&. However, the result does not have the correct data type or
gave errors in the evaluation:
Expression,,&V1&
ABAP type,,&V3&
Length,,&V4&

System Response

If no other valid agent (expression) was specified, the workflow has
been stopped and forced into the error status.

How to fix this error?

Correct the expression's definition/implementation so that it provides
a value with reference to the ABAP Dictionary structure <AB>SWHACTOR</>
(ABAP type: C14). In particular user names cannot be on their own here,
only with preceding organizational object type "US...".
Object references are not possible here either.
You can then continue a workflow that may have stopped with the
<LS>Restart After Error</> function.

Error message extract from SAP system. Copyright SAP SE.