Here is what I think is happening. I believe that New Outlook has some (AI like) features that are attaching files that it believes you may find helpful when creating Meetings. It is pulling those supposedly helpful items out of Sharepoint. Those items appear to retain their Sharepoint permissions meaning: If you create a meeting and add me as a participant and it adds two files but I only have permissions to one of those files, then I only see the file that I have permissions to. I have tested this but I do not know why it is attaching anything on its own. These attachments are on the meeting as soon as it is created. If I turn off new Outlook then create a meeting, there are no automatic attachments. If I have created a meeting in new Outlook and it has added said attachments and I switch back to old Outlook without deleting the meeting then the other participants will still see the attachments in their invitation as long as they are attachments that they had permissions to (per my earlier mention). I do not believe the Safe mode suggestion will provide any helpful information. I think this is a feature that is meant to be helpful but it was not executed in the best manner for customers. There is almost certainly a setting to be able to turn this feature off. I just need to know where it is.
I appreciate any help you can provide and I hope that these additional details will help toward identifying a resolution.