Q: Missing e-mails (Office 365 and Apple Mail)

Lately I've experienced quite a bit of issues with Office 365 e-mails disappearing and reappearing in my Mail client. This happened again today with an e-mail I know I looked at last Friday but today it's gone from my inbox. It does however show up in the Office 365 web UI so nothing's missing completely, only in Mail.

This has happened before too. That time the missing e-mail reappeared automatically again a few days later.

I've lined up the web UI with the Mail client, in both cases I've searched for e-mails from a particular sender. All but one are there. The Mail search is set to Show all.

If I try and search for the subject line of the missing e-mail, I find two fragments of the missing e-mail that's located in Files (whatever that is). The fragments are however without sender and are incomplete.

Has anyone experienced the same issue? Thinking about re-installing the account all together in Mail but if there's an easier solution it would be much appreciated!