Error HTTP 502(Chrome) specific website packet tracer invalid traffic

Hi everyone,

I really apreciate your support in this case.

We are using a Sophos XG 210(SFOS 17.1.1 MR-1). 

When we try to access the website www.eletrosul.gov.br(a brazil government website) using the static wan ip address(187.X.X.161/28) configured in the interface Port2, we get the error 502 in the browser.

Follow is the tcpdump(saved to wireshark):

If we changed the NAT outbound to use another IP in the same range as the Port2(ending in 163, the website access is fine. Follow screen:

Follow is the tcpdump(saved to wireshark):

We already contact the ISP.

The packet tracer shows "INVALID TRAFFIC" but no idea whats going on.

Any help, it would be very appreciate.

Thanks in regard,

Fernando Dias