Strange behavior: iMac 27" running Sonoma, Office 365 and Outlook crashes

So I volunteered to help someone that is fighting (and winning) cancer. They have an iMac (27") with Sonoma running. And office 365. Problem started two months ago that their Outlook would freeze or beach ball. Word, excel, ppt…all fine. Just Outlook.
I tried all the tricks and eventually ripped out Office 365, then re-installed. It appeared to work. Then, about 4-5days pass and it came back. Luckily, the user can get to, but to him, not as convenient nor “looks as functional” as the desktop app. I ran utility, ran malwarebytes (nothing, clean), I tried another profile, and again, ripped out anything associated with Microsoft. After a week, I get an email, doing same thing again.
Now, this iMac was migrated from an older mac and I can see remnants of older files. I was thinking of replacing the OS (perhaps something corrupt or problem) and just do the boot to recovery, re-install Mac OS and then rein-stall Office 365.
Searching MS forums (who else hates MS technical pages do redirects if your try to go back a page!) found a few with same problems but no resolution.
Atleast this person has another mac (MacbookPro) that office is working (x fingers) but its only outlook and scratching my head… if there is an email, or file or account problem or … ideas?

Don’t immediately jump to reinstalling the OS - it rarely fixes things because of the way the sealed system volume works. The problem is most likely in the Data partition where your user profile sits.

But, my first suspicion is that the problems might be due to some of the cruft/remnants of older versions. A quick way to check this out would be to create another macOS user and see if Outlook behaves the same way.

Then I’d sanitize any remnants of those old files by using Microsoft support articles such as f Uninstall Office for Mac - Microsoft Support

If you want to go down the “scorched earth” route, there’s no need to reinstall macOS Ventura or Sonoma through Recovery. Instead make sure you have a complete backup of the system and then use System Settings > General > Transfer or Reset > Erase all contents and settings. This will reset the Data partition as if you have a brand new Mac. Then run through the setup and create a new user. Don’t use the Migration Assistant to restore the users for you - that’s just going to repopulate the user’s Library folder and possible re-introduce the same problem that’s plaguing you now. You can bring back the Documents and other folders (such as the Music and Photos), but don’t blindly copy everything from the Library folder. Then, re-install the Microsoft 365 applications and see if things behave differently.

Thanks. Yeah, I was thinking of a new user to see if that works. Since he doesn’t have that much in way of files, I could always sneaker/copy his files over. And agree, something is affecting ONLY outlook. When you launch it, it would bounce…then stop. And after minute, error pop up to send to Apple. I was thinking, could it be bad ram, or some locked file. But I’m not able to decode the crash log/pop up.
Next time I see him, I will make another mac user. My only concern is his time, that he gets tired from treatment and putting up with me :slight_smile:
I had the same link to MS on the Uninstall. Wish there was a tool like the older versions…

This post has some advice about clearing Outlook caches:

And other tips here:

Apologies if you have already tried these