I'm going to jump in on this, as this just happened today. On Prem Exchange - Microsoft 365 Apps for Business. Exchange Account. Same as screen shot above, except for me, Outlook (that comes from Microsoft 365 Apps for Business which is NEITHER of the Outlook apps asked for above), froze up completely, then added the event 3x to my calendar.
For 2 weeks we have had nothing but problems from the Outlook that comes with Microsoft 365 Apps for Business, and are planning migration away from Microsoft Office completely. There is no reason that the apps should be crashing like this with on-prem servers for emails that aren't the least bit different than they have been the last 20 years.