Not too frequent, but shows up a few times.
#0 /srv/mediawiki/php-1.31.0-wmf.23/extensions/ReadingLists/src/Api/ApiReadingListsDeleteEntry.php(29): MediaWiki\Extensions\ReadingLists\ReadingListRepository->deleteListEntry(integer) #1 /srv/mediawiki/php-1.31.0-wmf.23/extensions/ReadingLists/src/Api/ApiReadingLists.php(46): MediaWiki\Extensions\ReadingLists\Api\ApiReadingListsDeleteEntry->execute() #2 /srv/mediawiki/php-1.31.0-wmf.23/includes/api/ApiMain.php(1580): MediaWiki\Extensions\ReadingLists\Api\ApiReadingLists->execute() #3 /srv/mediawiki/php-1.31.0-wmf.23/includes/api/ApiMain.php(542): ApiMain->executeAction() #4 /srv/mediawiki/php-1.31.0-wmf.23/includes/api/ApiMain.php(513): ApiMain->executeActionWithErrorHandling() #5 /srv/mediawiki/php-1.31.0-wmf.23/api.php(94): ApiMain->execute() #6 /srv/mediawiki/w/api.php(3): include(string) #7 {main}