PhotoFlow freaks out when it has to display too many pixels

[CarVac]

Version: 0.2.4-1dhor~vivid

With 1:1 view on my 4k screen, less than half of what should be visible in the photo actually gets painted. The rest is either black or gibberish.

See photo:

http://i.imgur.com/W6snk8p.jpg

If I zoom out once, all but the very top gets painted correctly.

If I zoom out to fit (smaller than that), the whole image is visible.