Interesting is that the type and name tags are initial. This means that the context of the check (type=HS, name=<ws_name>) are not known (perhaps because it is not in USOBHASH yet?).
I think you should open a customer message and report it to SAP. I suspect that when trying to get the <ws_name> from usobhash using the webservice hash, it is also clearing the authorization data fields. Just a guess though - wouldn't bet my hat on it.. :-)
Cheers,
Julius