[Semibug] OpenVPN hates ssh

[Mike Wayne]

I'm hoping someone can suggest where I should look to debug this. Here's the
setup:

   FreeBSD client---EdgeRouter 1 (OpenVPN version 2.4.0)---FreeBSD server #1 (OpenVPN version 2.4.8)   Fails
   FreeBSD client------------------------------------------FreeBSD server #1 (via public IP)           Works
   FreeBSD client---Edgerouter 2 (OpenVPN version 2.3.2)---FreeBSD server #2 (OpenVPN version 2.4.4)   Works

In all of the above the client is the same.

The problem is that ssh is timing out after ~55 seconds. Nothing in the
openVPN logs. The link remains up and running; if I ping, it is not
interrupted.

I do not think it's MTU because it happens even with no traffic
going across the link, just sitting at a shell prompt after login.

It >feels< like an ssh timeout issue but I can't figure out where I
should look to start to debug it. 

Any thoughts?