Using New Outlook on Windows for professional communication and productivity
My workaround, as the problem only seems to show up when using iCloud, is using agenda from iCloud. I have the agenda from Outlook next to Outlook/agenda on my screen. Instead of entering/changing whatever in Outlook/Agenda i enter/change it in iCloud/Agenda. A few seconds later it shows up in Outlook/Agenda.
I installed everything on a new laptop: same problem, same workaround.
And yes, installing 16bit Office365 does not have that problem.