Created Unassigned: Blit gives inconsistent results when enlarging [21275]

If I call Blit with a target rectangle that's exactly 3x the size of the source rectangle, I would expect the result to contain consistent, blocky, 3x3 "pixels". Instead, I get a crazy mishmash of 2x2, 2x3, 2x4, 3x2, 3x3, 3x4, 4x2, 4x3, and 4x4 "pixels" in the output.

Repro (using the latest NuGet package, 1.0.12.0):

var source = BitmapFactory.New(8, 8);
// Generate a checkerboard of pixels
for (var y = 0; y < source.Height; ++y)
for (var x = 0; x < source.Width; ++x)
source.SetPixel(x, y, ((x ^ y) & 1) == 1 ? Colors.Black : Colors.White);
// Enlarge to 3x
var target = BitmapFactory.New(source.PixelWidth * 3, source.PixelHeight * 3);
target.Blit(new Rect(0, 0, target.Width, target.Height), source,
new Rect(0, 0, source.Width, source.Height));
// Display the result
MyImage.Source = target;

Expected: a nice even checkerboard. Every square in the output should be 3 pixels wide and 3 pixels tall.

Actual: the row heights are 3, 4, 2, 3, 4, 3, 3, 2. Same kind of crazy variation on column widths. See attachment.