Setters and getters for entityId are removed in platform 6.8.0 ProcInstance. However in 6.8.0 BPM documentation section 6.1 Starting process programatically it calls ‘procInstance.setEntityId’ which no longer exists.
There maybe similar issues elsewhere but I have not gone through all. This causes problem when upgrading from 6.7.9 to 6.8.0. Please update documentation so that we can update our code accordingly.