"It is not clear if the DTR app is saving its context to a single payer which is responsible for maintaining the app, or is it saving it to any payer server it wants to that uses that app. How the DTR server gains access to the payer server is an open question right now. But is just a black box. It doesn't particularly matter how it gets done. We welcome feedback on how this process should or could work."

The information MUST be written to the same server from which the Questionnaire was sourced (on which the $questionnaire-for-order was invoked).  And the means for gaining access to persist the DocumentReference is the same as that used to gain access to that operation (and possibly the $next-question operation).  Please remove the STU note and ensure these expectations are reflected in the spec.