Invalid value in reference field (internal syntax error)

What causes this issue?

The <LS>MASTERTYPE</> reference field has not been filled correctly for
an object key (E071K).
The current value is &V1&, however only the following (table type)
object types are allowed for the <LS>MASTERTYPE</> reference field:
MASTERTYPE
CDAT
TABU
TDAT
VDAT.

System Response

The function terminates.

How to fix this error?

You cannot fill the <LS>MASTERTYPE</> field manually. If the error
occurs again, contact the Hotline of the application where it occurs.

Error message extract from SAP system. Copyright SAP SE.