SAPF150D2 PARAMETERS_INVALID

When running a F150 dunning run the printout terminates with following error:

A RAISE statement in program "SAPLFTOOL_FORMS" has raised exception condition "PARAMETERS_INVALID".

If the error occurs in a non-modfied SAP program, you might be able to
find a solution in the SAP Notes system. If you have access to the SAP
Notes system, check there first using the following keywords:
"RAISE_EXCEPTION"
"SAPLFTOOL_FORMS" bzw. LFTOOL_FORMSU01
"FORM_CHECK"
or
"SAPLFTOOL_FORMS" PARAMETERS_INVALID
or
"SAPF150D2" "PARAMETERS_INVALID"

When I debug the dunning run the MHNK is filled with a customer that has a payment block "R". That is kind of suspicious.

Here the log output for this customer:

Does someone have a clue?

-----

Forms are defined correctly in my opinion.