Problem with declaration for &1; too many &4 declared

What causes this issue?

The declaration for &V1& arises a problem because not all information
gained during the declaration run can be transfered to the interface of
the Dual System.

System Response

The interface of the Dual System only allows a limited number of &V1&s
being transfered. The &V1& to be declared exceed this number. Since not
the complete information could be transferred, the declaration was not
processed correctly.

Error message extract from SAP system. Copyright SAP SE.