Comment 7 for bug 514649

It appears to be a problem with how the file is sliced up during export rather than a multithreading issue. Disabling multithreading didn't help (at least on my machine) while the image did come out alright when I specified that the export should be done in just one go (see attachment). This is a very old problem and I'll have a look to see why it reared its ugly head again.

I also think I saw some issues when zooming out though, so I might get back to that later. (This image is very interesting for testing blur as it has very sharp and large discontinuities in very irregular patterns.)