SDM and Catalog are integrated on different ways. Several parts of the integration are utilizing function calls which are retrieving server config details defined by the administrator in SC's "Configuration" settings .
There is one single set of configuration values which is utilized for Web-Frontend calls same as for Webservices usage (function "openSDMClient" in requestshared.xsl)
In environments where Web-Frontend and Web-Services access is configured different environments, the configuration setting will work for one or the other, but not for both.
Extend the configuration parameters to differentiate settings for webservice and gui to allow appropriate configuration.
(by now, affected parties are editing the function call not mapped properly by the configuration parameter).