The update introduced, and set as default, a version 2 lens correction profile for the Canon RF24-240 lens which causes the Raw image to display incorrectly by showing an area outside that of the matching camera Jpeg which is blurred and distorted (I have only found this for images shot at zooms of 38mm upwards). This region can of course be cropped out as it is not part of the intended image. Reversion to the previous profile removes the problem.
The Max 2021 Photography products updates have been released and include remedies for this topic.The updates will be rolling out worldwide, October 26 and 27, 2021. If you do not see the updates in your Creative Cloud Desktop app, you can refresh the apps to see if the updates are available in your region.The keyboard shortcut to refresh is [Cmd/Ctrl] + [Opt/Alt] + [ R ].
Note: iOS and Android updates may take up to a week to appear in your App Store.
Thanks for the help. The problem was caused by the V2 lens profile for the Canon RF24-240. By using the original version of the profile everything was fine. Doing a mass change was easy in LR. I selected all the photos taken with the RF24-240 lens, then in develop module with "auto sync" enabled I choose the original lens profile and auto sync updated all the images.