With Dynamic Business Orchestrator, when branching or merging processes, you must use gateways, for example:

In this example, Gateway 1 introduces two run-time rules, "start_1/name=foo" and "start_1/name=bar", which enforce that at least one live sequence flow will get executed. If the sequence flow fails, the process model will fail at Gateway 2, instead of Task 3. The gateways help troubleshoot which flow causes the failure and re-adjust the process model accordingly.