These commands seem to fix a lot of problems that creep into Outlook.
Open a Command Prompt to your Office install directory. For Office365 in 2019 it is the following:
C:\Program Files (x86)\Microsoft Office\root\Office16
cmd with the desired command below. It will open Outlook having performed the desired command.
|resetfolders||Fixes issues with Outlook automatically updating and refreshing mail and other items.|
|cleanreminders||Fixes issues with Outlook processing reminders and other tasks.|