Bridge Not Forwarding ARP

[Dan Lists]

I have a server running FreeBSD 11.2 that I am wanting to use as a bridged
firewall.  I have it set up and it mostly works.   The problem is that ARP
replies are not being forwarded from the outside interface to the inside
interface.   It appears to be working in the other direction.  I see the
ARP request go out on the outside interface and the reply arrives back at
the outside interface.   The ARP reply is never getting to the bridge or to
the inside interface.

The firewall server and the device behind it are in ESX.   I think I've
worked all the ESX issues out.  When I manually add an ARP entry everything
works.   I've done this before with a physical server running FreeBSD 8.4
and it works as expected.   The differences are physical vs virtual, and
8.4 vs 11.2.

I'm at a loss as to why it is not working.   I've searched the web and
found noting.  If anyone could offer suggestions on how to fix this or
begin to debug it I would greatly appreciate it.

Thanks,

Dan