If an error occurs within a service that the SwitchYardServiceTaskHandler executes, the process continues, and there isn't a way to access a fault object so that a conditional path can be taken.
There are two things that should be investigated as options here:
1) Add the exception to the results variables so a conditional gateway can be used.
2) Have the SwitchYardServiceTaskHandler wrap the exception/fault and use that as an event to signal the process with. That way an error path can be defined in the process.