Using Classic Outlook on Windows for personal email, calendar, and contact management
The Outlook Team had a bug with this issue previously. It was fixed in version 16.0.13001.10000. What version is your Outlook (File, Office Account, under About Outlook)?
If you have a version higher than above it should be fixed. Its possible there is a new issue though if you are still seeing it. In case you have the option to open a ticket click Help, Contact Support. Not everyone has that but please check if you do.