Action box customizing does not support processing mode &1

What causes this issue?

The function module 'EWA_S_FOCONFIG_MAINTAIN' for customizing the
action box was called up with an invalid processing mode.
The invalid processing mode was '&V1&'.
This is a real program error.

System Response

The program is terminated with a runtime error.

How to fix this error?

Correct your program or contact SAP with this message if this concerns
a program delivered by SAP.

Error message extract from SAP system. Copyright SAP SE.