Using Classic Outlook on Windows for personal email, calendar, and contact management
Stuart,
There is no fix yet. The Outlook In App Team has been trying to get traces that development needs to investigate the issue but we have not gotten that yet. If you have the option to open an In App ticket, please do. To do so click Help, Contact Support until you see logs are submitted. If you don't have this option but willing to open a ticket let me know and I will contact, you via forum moderation and enable you for Contact Support. Not everyone has the Contact Support option. Its slowly being made available and currently at Tenant Admins, Insiders, and some Consumers.