I’m also experiencing this error (noticed it for the first time on 27 Oct 2023). It appeared on all 4 of the websites I’ve set up, which are all using the Astra theme. I can work around it by switching permalinks to Plain to do page editing and then switching back (to Post Name) when I’m done.
I’ve tried on a sandbox site with *all* plugins disabled. With Astra theme, I can only add/update pages if Settings -> Permalinks is set to “Plain”. Changing theme to 2024, there is no problem (all permalink formats work). I repeated this exercise several times with consistent results.
