There was a bug in older mw where upload log entry was made before page creation, so it did not have the page id. So many older upload log entries are like this if the page didnt exist prior to upload.

I think there's a different bug going on here.

The problem seems rather infrequent: 249 out of 58568 uploads since Jan 1 on Commons. And the ones I spot-checked show multiple uploads at about the same time, which makes me suspect that what might be happening is that users are clicking "upload" twice, LocalFile::recordUpload2 is managing to get $exists == false for both, but then one of the calls to $wikiPage->doEditContent fails (so mArticleID in the Title object never gets updated), and recordUpload2 never checks for this failure.

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