Well, this is kind of worrying… files are not supposed to be just accidentally truncated. The original upload of https://commons.wikimedia.org/wiki/File:Otto_E._F._Grashof_-_Parada_en_el_campo.png was apparently cut off after exactly 35 MB, the full size is 37.59 MB.

There could be a problem with UploadWizard, or with chunked uploading (UW uploads files in chunks of 5 MB), or with AssembleUploadChunks or PublishStashedFile jobs (UW uses async uploads for files over 10 MB).

However, I couldn't reproduce this problem when uploading the complete file neither locally, or to Commons (I stopped before publishing, but verified that the whole file was in stash and could be thumbnailed, and it was identified as a duplicate of the existing one). Perhaps something messed up the file on your side, or perhaps it's the elusive server pixies.

I also tried searching logstash for the file name, hoping to find something interesting, but I only found lots of "Removing bad 0-byte thumbnail" entries for all the failed thumbnailing attempts.

@Zeroth Please make sure to file a bug if you ever notice this happening again.