The component upgrade jira for Narayana 5.9.6.Final (https://issues.jboss.org/browse/JBEAP-17321) provided fixes for XTS JTA transaction bridging. Those fixes were necessary because of upgrade of the WFTC component.
The WildFLY contains tests for the fix. Those tests should be backported to the EAP7 branch.
(the WFLY PR for tests is here https://github.com/wildfly/wildfly/pull/12197/files)