Argument should be persistent according to error text, but is triggered is said argument is persistant.

[Sluimers]

Dataservices.java

if (targetArgName == null || viewArgName == null || Core.getMetaObject(viewArgType).isPersistable())
            throw new RuntimeException("Microflow '" + serviceDef.getOnUpdateMicroflow() + "' should have one argument of type "
                                       + serviceDef.getSourceEntity() + ", and one argument typed with an persistent entity");