Exit & has the incorrect type

What causes this issue?

The exit type of the system exit or user exit cannot be used in this
condition.
This may be the case, if:
in a condition, you have used a user exit that does not match your
validation or substitution callup point.
&BEISPIEL& In FI, you cannot use a
user exit
that refers to the complete document structure for callup point
"document line".
in the substitution, you have used a user exit whose definition of the
parameters (in the FORM routine GET_EXIT_TITLES) does not coincide with
how it is used.
&BEISPIEL& If you select the option "Only exit" when choosing the
substitution fields,
you cannot enter a user exit that is defined with a parameter.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

How to fix this error?

Use a different exit or check the definition in the exit form pool.
The routine GET_EXIT_TITLES in the form pool specifies the exit type.

Error message extract from SAP system. Copyright SAP SE.