Irregular line appears when making mosaic

hello all,
I make a mosaic composed of 168 pictures.
As you can see in the patch I use resample and cross to generate coordinates of pictures. here’s the problem: vertical black lines appear on the image. I tried every resample modes but it doesn’t change anything…
do you have any idea of what it would come from ?

And second point: there’s a canvas of 140 x 120 pixels: horizontal white lines appear when you toggle animation (different alpha color of pixels).
Maybe the same problem ?
Hope I’m clear: here’s pictures and patch.

debug grid.v4p (969.2 kB)

I think that’s being caused by aliasing on the Renderer.

If I change some of the scale values I get this pattern:

thanks, didn’t think about that…it must be a directx9 issue ?