The policy is failing when running on CloudHub/API Portal

[trknz]

CloudHub, AG 2.2.0 Tried applying the policy on an API. The below response is produced

Execution of the expression "                                       
                                        app.registry['lock'].lock();
                                        if (!app.registry['sn'].contains(key))
                                            app.registry['sn'].store(key, payloadBck);
                                        app.registry['lock'].unlock();                                      
                                        " failed. (org.mule.api.expression.ExpressionRuntimeException). Message payload is of type: String

:

[jonathanptew]

I get this same issue with the Response Caching Policy on the On Prem version of AG 2.2.0.