I would test it until it breaks or it fixes by testing out various combinations of background properties and border-radius.
It looks like the bug is triggered when the background-position horizontal position is less than -1px (i.e. -2px and above) and background-repeat is set to none and border-radius is also set. Looking around the web there seem to be similar bug reports for gradients and zooming images.
I’m also assuming that odd image sizes may have something to do with it as mentioned in the other thread but are not pertinent to this example…
Adding the background-clip:padding-box seems to fix it for all occasions.