On Mon, Sep 10, 2012 at 10:24 PM, Erik Moeller erik@wikimedia.org wrote:
No, it's not normal; it's a bug with thumbnail generation on the cluster. See https://bugzilla.wikimedia.org/show_bug.cgi?id=39975 if you're interested in the technical details.
This turned out to be pretty hairy, sorry for the long time it took to get it resolved. It should now finally be fixed; please let me know if you're still seeing it.