under what conditions would proxy rights on an account not be returned by
SOAP but would be by the ObjectAPI?

We have a situation where quite a few accounts do not show *any* proxy
entries (not even <All User Access>) in the response from
getProxyAccessListRequest() using SOAP.
Several even do not show specific user proxy entries.

However, when we use the object API, with the same trusted key, *all*
accounts show the <All User Access> entry, and the specific user proxy
rights are returned as well.

At this point, we no longer trust the SOAP proxy call. What might be the
cause of this? Can this be fixed?
(POA is 7.0.3HP1, running on SLES10.1)