Using the New Outlook for Mac for personal email and calendar
Solution: Switch to legacy mode and straight back again and the issue should resolve itself. I also noted that clicking the TaskPane causes the issue in the first place. Definitely a change that MS introduced as it wasn't an issue before and the fact that so many people are reporting it smacks of a bug introduced along the way. It is NOTHING to do with the resolution of the screen or accessibility or anything else. MS need to work this issue out for its users and not waste their time suggesting we are all idiots.