Microsoft 365 Outlook Is Losing Appointments

I am running Windows 11 Pro version 25H2 but the problem I Am Having was the same on version 24H2. I use Microsoft 365 for all my office products including Outlook. A few weeks back I did a lot of trouble shooting but apparently not enough or the wrong ones. I ended up having the fellow who can remote into my computers remove Outlook and then reinstall it. We created a new PST file to be used on the profile that is the problem. This only is happening on 1 computer. It is losing scheduled appointments from the Calendar. After reinstalling Outlook, we thought all was well. 2 days ago, my wife printed out 2 months worth of calendar appointments using the Monthly view. After we got home from setting up 10 more appointments, she went to put them on her calendar and send me a meeting notice so I would have the appointments on my Outlook calendar. She noticed that 2 appoints had disappeared from her calendar even though only 2 hours earlier they were there when she printed out the Monthly view. This is the reason we started new with Outlook on her machine. Any suggestions how to keep her Outlook from losing appointments would be appreciated. Not sure it matters but SCANPST.EXE was run.

Thanks