Firewall ( SFOS 20 ) block url with 502 bad gateway

Hi there,

we want to open the url: https://procurement.cern.ch and get the error: 502 Bad Gateway.

If I open the URL without our firewall ( at home...) the website will open !

So the problem is our Firewall with SFOS 20.0.0 GA Build 222.

I also tried it with "none" web-policy but I got the same error because I found KB-000035989

Any idea where I can resolve the error?

I also tested the url on ssllabs.com and get A+ ( very good )

many thanks

Thomas