It seems that the error pop-up rather seldom, and has been doing so
for over a decade on the forum. My gues it that it can’t write to the DB due to a temporary lock of some sort. These things normally get cleared rather quickly and kind of "self-cure" (well, rather, the DB engine takes care of it).
Normally it can occur when there are multiple simultaneous petition that need to access the same internal database page (i.e. concurrent write petitions, a longish read process that escalates to a page or table lock for a few seconds, and so forth).
Yeah, I run into errors like this quite frequently, and without really looking into it, I suspected it would be along these lines. Especially, when you're doing things quickly, it seems to happen a little more frequently, or taking actions which take a lot longer, like deleting a lot of replies at once.
I never contacted anyone about it, since I suspected that every staff user runs into the error, as I'm not doing anything particularly out of the ordinary. I don't think I've ever run into it outside of that though, except when maybe the old statistics were available to view, but they've been long disabled now.