Problem when attempting to route between two route domains.

Check this:

https://support.f5.com/csp/article/K84417414

Have you created the correct static route in the two route domains and also better enable strick isolation as the parent child relationship will still work and this way the traffic will not go to a wrong domain.

Check with the tcpdump if the request are exiting in the correct route domain and if you see the return traffic. Maybe it will be needed to create a static path also for the return traffic?

https://support.f5.com/csp/article/K6546