Ok, what's the error? can you share the stack trace? Can you let us know which version of MySQL are you using, under which operating system?
This is caused due to both runtime engine and bam module share the same persistence unit and if you have there ddl generation set to create it will rebuild the schema every time entity manager factory is created, meaning two time: first time when you build the session and then when the bam module is initialized for instance when you view process instances in the console.
So your conclusion is right, setting it to update is the right setting.