It appears that the metrics is not using a isolated transaction.

Discussion: Should it be using an isolated transaction, i.e. a new Hibernate session than the one used by the code servicing the request?

Observations: Mapping errors in other parts of the code were triggering updates on dirty objects. The code servicing the request were purely read only. The metrics starts a write transaction picking up the same session and triggered a flush of objects unrelated to metrics processing. One one hand this identified some problems in other parts of the application. However it is not clear if the metrics should be triggering updates on unrelated objects.