I used cp4052 to test out this issue so what i can tell so for is when the IDRAC is at version 5.10.30, the IDRAC.WebServer.HostHeaderCheck value is 0=disable and when upgrading to version 5.10.50 and 6.0.02 that value changes to 1=enable.
The quick work around to get back the UI working is to login to IDRAC and run the command

racadm set IDRAC.WeServer.HostHeaderCheck 0

Long term solution:
@Volans @jbond is it possible after the IDRAC version is at 6.0.02 to reset IDRAC.WeServer.HostHeaderCheck to 0 with the firmware upgrade cookbook. check if IDRAV version >=5.10.50 set IDRAC.WeServer.HostHeaderCheck to 0.
or if you have another solution for this .

Thanks

@Papaul i think we have fixed this issue by ensuring the redfish spicerack module uses the management ip address and no the hostname. Can you confirm?

I had a chat with @jbond on IRC he is looking into this.

notes to self we can set the DNSRacName with

pp(r.request('patch', '/redfish/v1/Managers/iDRAC.Embedded.1/EthernetInterfaces/NIC.1', json={'HostName' : 'sretest1001'}).json())

Change 857740 had a related patch set uploaded (by Jbond; author: John Bond):

[operations/software/spicerack@master] redfish: Add reboot message id for new idrac versions

https://gerrit.wikimedia.org/r/857740

Change 857740 merged by jenkins-bot:

[operations/software/spicerack@master] redfish: Add reboot message id for new idrac versions

https://gerrit.wikimedia.org/r/857740