"InvalidClassException: org.drools.rule.MVELDialectRuntimeData" when a WS tried to retrieve a PKG from BRMS 5 server

Issue

A web service is failing when it tries to retrieve the PKG from BRMS 5 with the following error:

java.io.InvalidClassException: org.drools.rule.MVELDialectRuntimeData; local class incompatible: stream classdesc serialVersionUID = -5592039914251136412, local class serialVersionUID = 5166066541265170937

BRMS 5.3.1 runs on a different server than the web-service is deployed to. Using a KnowledgeAgent to establish connectivity.
The client libraries are 5.3.1 and so is the server. Both client and server uses JDK 1.7. The applyChangeSet is what causes the failure:

kagent.applyChangeSet(ResourceFactory.newUrlResource(guvnorUrl));