Paul Stansell <paulstansell@gmail.com> writes:

>>
>> May it be that you often have multiple Emacs processes running
>> simultaneously and killed by signal?
>
> I do typically have multiple Emacs processes running simultaneously, but
> I'm not aware that I kill Emacs processes, I either quit Emacs with C-x
> C-c, or I click on the "X" in the top right of the window.  Could the
> latter be sending a kill signal?

No idea :)
In any case, your errors look like some kind of mixed state from
multiple Emacs sessions writing to the same cache file.
May you try the attached patch?

> ... By the way, I've exited Emacs by clicking
> the "X" for years, but I've only recently noticed the warnings.  Also, if I
> switch to using the version of Org Mode that comes with the distribution
> (Kubuntu 22.04), instead of using the recent one from a git clone, I don't
> think I get the warmings.

That's because disk cache has been introduced in the recent Org mode
versions.

-- 
Ihor Radchenko // yantar92,
Org mode maintainer,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>