The HU belonging to SU &1 does not exist in WM-managed stock

What causes this issue?

The handling unit (HU) &V1& that belongs to the storage unit (SUn)
exists in the system, but not in a HU-managed storage location. This
does not necessarily mean that there is a quantity difference between
the two objects. It is more likely that the stock data is different.

System Response

In this case, the system cannot automatically adjust the handling unit.

How to fix this error?

Correct the inconsistency by performing an IM/WM issue posting.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.