I debugged the FM and found that in form check_adm, there is a check:
*& checks if the ADM data is set
*& (e.g. UDO writes this data empty or with old named codes)
if l_adm-actcode CN ' 0123456789' or
l_adm-mencode CN ' 0123456789' or
l_adm-pfkcode CN ' 0123456789'.
p_not_ok = 'X'.
endif.
In my case, l_adm-actcode contains value X, which I suppose is an old code that is no longer accepted.
So my guess is that (at least internally) the PFSTATUS system has changed in the latest NW version, and Saplink needs to be updated to be compatible with this change.