Actually, if that's even the proper address it was trying to connect to. Oddly, part of your error message states:
'https://server.domain.fi/niku/xog'.server.domain.fi
Like it is all part of the address it is trying to use, though that may have been an oddity in the logging. Check the <soap:invoke> tags and see if they are doing any appending to the endpoint= attribute, like <soap:invoke endpoint="${some_var}.server.domain.fi" ...>
The some_var could be from a <gel:parameter /> tag, which is then having its value set from the process step's Custom Script Parameters page in the UI. If you don't get any luck pinpointing the problem from that, if I could see the script and the endpoint parameter value, it could help (masking out any xog user passwords that might be left in the script itself first).
Edit: Also if that message was found from the Clarity UI, the full version of it in the bg-ca / bg-niku log files would be of value too, in case there are nested exceptions further down past this point that just bubbled up to this conclusion.