Special stock & not defined

What causes this issue?

The special stock indicator &V1& is not defined in the system.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

When you press F4 in the field "<GL:special_stock>special stock</>",
a list of valid special stock indicators or valid movement types
including the relevant special stock indicators is displayed.

Error message extract from SAP system. Copyright SAP SE.