Hi,@Michael Wiskman
Thanks for posting your question in the Microsoft Q&A forum.
When you run Get-Federationtrust | Set-FederationTrust –RefreshMetadata, it says that the command completed successfully, but no settings of 'Microsoft Federation Gateway' have been modified. This is expected behavior, you just need to wait 24 hours for the command to be modified.
Regarding the issue where users got a lot of Event 2008 after recreating the oauth certificates, I found that other users also reported this problem. This is an event that can be ignored and will not affect user .It is recommended that you run Get-Federationtrust | Set-FederationTrust –RefreshMetadata to temporarily stop the message.
Here is what other users are saying: Event ID 2008 warning from Event Source MSExchange OAuth appearing randomly - Microsoft Q&A
If my answer is helpful to you, please mark it as the answer so that other users can refer to it. Thank you for your support and understanding.