Calendar forgetting bookings

I’m doing a lot of testing and it’s odd.
So let’s say I book 8am on 8th July, office, community group.
It works. I get the email, so does admin, and if you check the calendar it’s there.
However when I go to a fresh browser (just to ensure there’s no caching issue) I go to book e.g. 9am, I notice I can also book 8am and viewing the calendar, the previous entry has vanished.
Why would bookings be vanishing from the calendar? Thanks

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