Business Process (BPL) scope and empty request/response objects

In a Business Process (BPL) I noticed that if I 'm using a "scope" to handle errors  then inside the "scope" when a "call" is used, the "request" and "response" action (i.e set for callrequest.prop = request.prop & response.prop = callrespones.prop does NOT work !
The result is that the values of those properties in the callrequest  are nulls (I do see the properties names in the content of the callrequest message)

What is the best way to solve this issue ?
As it seems that there are new instances of the request/response objects inside the scope, whats the best way to pass them into the scope ?
Is there a better custom error handling than using scope ?

regards.

yaron