These are some I had over the last few months actually;

"I can't save outside of onedrive"

"My mails aren't getting delivered"

"My office suite has deactivated itself and won't reactivate"

"We need a shared mailbox for x,y,z"

"The new joiner can't access my onedrive/shared drive" (No groups/auto-groups - they require some more advanced administration or discipline).

"I received an email from someone impersonating the CEO asking for an invoice to be paid immediately"

"My Excel sheet is somehow not syncing to onedrive and now there's conflicts"

FD: We don't use Teams, and we migrated from o365 to GSuite, but there are some people who remain on o365 for Office reasons.

Teams won’t display any usernames for an external company that added to me their chat, everyone is Unknown. Maybe misconfig, something to do with cross domain permissions, but it feels buggy and broke.

Excel has some funk around keeping shared files in sync. We set up one spreadsheet where I have read only access so I don’t accidentally delete anything. Turns out when I do make a change, excel creates a locally cached version and stops syncing changes. That took a couple hours of screwing around to figure out, and the solution was to duplicate the spreadsheet with a new name and delete the old one.

For teams there was a month where every single call it would lag out for 5+ seconds every minute or more. Just completely unusable.