UDP network with --net=host doesn't work as expected

I have an application that sends out & listens to UDP packets. As such I have two containers that talk to each other over UDPv4. When I run these applications on the docker host directly, they talk fine. When I run them as containers with --net=host, they can’t talk to each other.

I did attempt to create a new docker network with macvlan and assign each container an IP and that allowed the application to work also. Now I’d rather not have to use macvlan.

My current thinking is that the UDP packets are getting fragmented and not put together properly. Any other ideas on why they aren’t working properly? Suggestions on how to diagnose this right?