Action manager: Enter 'X' or SPACE for parameter &1

What causes this issue?

The action manager was called up with an invalid value for the
parameter &V1&. Only the values 'X' or ' ' are possible.

System Response

The action manager cannot perform the required task.

How to fix this error?

The program including the action manager must be corrected.
Contact the program author - if the program involves one delivered by
SAP, contact SAP.

Error message extract from SAP system. Copyright SAP SE.