Though note that the results still work if the URL is directly searched like this:
/search/?q=sort:date&page=3
Gut: It has to do with I manipulate the query to run some of the SERP myself before sending (or even in lieu of sending to Lunr.js). That leads me to spotting this issue where the next button works (though sort:date is omitted) but then the previous button fails, from here: /search/?q=test&page=2
2023-09-05 16:12:58
back-to
for pposts currently says: type:post rather than cat:ppost2023-09-06 12:03:25
2023-09-06 13:59:55