Dear Aaron Izzard
Good morning! Thank you for posting to the Microsoft Community. We are happy to help you!
Based on your description, since your problem is occurring in OWA, please first kindly try clearing the cache of the browser you are using to check the results. If that doesn't work, please kindly switch to a different browser and log in to OWA in private mode (Incognito mode) to check the results.
If your problem persists, given that your problem occurs on OWA (Outlook web app), this indicates that the problem is most likely in the Exchange server backend, because our forum lacks relevant knowledge and permissions, so to better help you and not waste more time, please kindly try to create a service ticket in the Microsoft 365 admin center to support > service requests through navigation, as they have more access permissions than on this forum, and professional engineers will further help you.
Note: if you are not using admin account, please kindly ask admin within your organization for help.
Thank you in advance for your understanding! Your patience and cooperation will be greatly appreciated. Hope all the best!
Sincerely
Kerry Chen | Microsoft Community Moderator