We have resolved this issue.
From the example provided above, when the traffic arrives at Edge #2, it does not have
We found the issue.
The edge routers were dropping inbound TCP packets even though there was a firewall rule allowing them.
Digging into the pfSense documentation, we discovered that a firewall rule allowing TCP only allows TCP with a SYN flag set. Any other TCP packet is dropped. Additionally, we found that there is a default deny on traffic leaving the firewall (out direction) for TCP packets without a SYN flag set.
Normally, TCP traffic is handled by the state after the initial SYN packet.
Because the traffic was returning via a different edge router, there was no state established AND the firewall rule was allow all TCP traffic that had a SYN flag; the return traffic did not pass.
Adding two floating rules fixed the issue.
Allow TCP traffic was set to allow all TCP flags inbound (of course, only for traffic you actually want to allow).
A rule that allowed all TCP flags OUT of the interval interface (again, matching the traffic you wanted to pass).