&3' is not permitted as a link indicator for the node with the ID &1

What causes this issue?

The node with ID &V1& occupies the value &V3& as a link indicator. Only
the values 'X' and ' ' are allowed as link indicators in order to
indicate whether or not a node is a link.

System Response

The hierarchy cannot be loaded or activated.

How to fix this error?

Correct the link indicator in the source system or in the file.

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.