Hi @Cederpants ,
Welcome to Q&A forum!
This is the latest update released in September. If you have this problem after installing this update, it is probably caused by this update. There is not much information available on this issue. Have you checked the ULS logs to see if there is any abnormal information? If there is no information available from the ULS logs, we recommend that you go to the website (https://support.microsoft.com/en-sg/help/4051701/global-customer-service-phone-numbers) to find related number and call it to create a new Phone Service Request to Microsoft Phone Support team to see if they can find the root cause. Alternatively, they can delete the update and wait for the next update to fix this problem before installing the latest update.
Good day!
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