DB Transaction is not rolled back in classification editor

    private class DefaultSessionWrapper implements MCRSessionWrapper {
        @Override
        public <T extends OperationInSession> T wrap(T op) {
            if (!MCRSessionMgr.getCurrentSession().isTransactionActive()) {
                MCRSessionMgr.getCurrentSession().beginTransaction();
            }
            try {
                op.run();
            } finally {
                //no error handling at all
                MCRSessionMgr.getCurrentSession().commitTransaction();
            }
            return op;
        }

    }