I'm not sure where this is supposed to go, I didn't see a forum for it. We upgraded Exchange 2019 to CU12 this weened, and now sender based routing is not reading the header or from information properly. Our rules are set in a combination of the sender address and a header written by a transport rule.

Checking the header details, both the sender and the header show up in the message, but checking the SBR log, for that rule, we get the following:
12:16:41.247 [Verbose] Test dead loop condition ...
12:16:41.247 [Verbose] Test sender condition ...
12:16:41.247 [Verbose] Test header condition ...
12:16:41.247 [Verbose] Current header condition is: ExistsOne
12:16:41.247 [Verbose] Search header X-Reroute-Message-Zix: yes
12:16:41.247 [Verbose] header name not found, go to next ...
12:16:41.247 [Verbose] header not matched, return False
12:16:41.247 [Verbose] Header condition doesn't match, go to next rule

But both the sender and header condition exist on the message. I need to get this fixed ASAP.