Problem with UDS OPC connecting to RSLinx OPC Server

We're experiencing issues with the response time for our OPC UDSs fetching data from RSLinx. The problem is that for each tag configured in UDS Admin the OPC UDSs subscribes to the RSLinx OPC server, retrieves the tag data, and promptly unsubscribes, which is unlike any other OPC client we've tried. Retrieving data from 30 tags takes roughly 150 seconds using the OPC UDS, while a regular OPC client does the same job in 200ms. Is there any configuration parameter available to modify this behaviour?

thanks

Lionel