That’s really interesting, I chatted to support about it too and have to say got nowhere…
I did discover that Google have recently implemented a core update (https://status.search.google.com/products/rGHU1u87FJnkP6W2GwMi/history), so not sure if that had an bearing on it, we did discover we had another issue but still not sure if that contributed or not - waiting for further feedback on this.
I will update here if I have any further information and hopefully between us we can get to the bottom of it!