The same problem has been reported and fixed in jbpm https://issues.redhat.com/plugins/servlet/mobile#issue/RHBPMS-4621.

The same issue occurs in springboot application with rhpam 7. Under high load, transaction timeouts are detected and arjuna marks them for rollback. Then, Jbpm executor thread reuse the same transaction and throws a repetitive exception "No active transaction...".

I think that the same fix done for JtaTransactionManager in RHBPMS-4621 is needed for KieSpringTransactionManager.