Why are many calendar events disappearing?

Why are many calendar events just disappearing? This has been happening for the last three months!! Calendar events were there yesterday, are gone today! I tried in protected mode and lost even more events. Now even more are missing. Several I have re-input over the last months, and they get gone too. What’s going on!! There are no addons, no sync. Nothing but Thunderbird. any one else having this bug?? What file are events stored in and how do I read them?? Any way to recover anyof these?? There is a lot of information and annotations, such as cancellations and rescheduleing and the whole bunch just disappeared? Many older events are still intact but I sure don't know for how long!!! My profile is on a separate drive and is accesed by both W10 and 11 for email and calendar. No problems except they are missing using either system!! It's a bug!! Anyone interested in looking at it?? Robert [edited email from community support forum]