Tiling a background

Hi! I have a repeater that is exactly 981px wide.

For this I’ve made this background, that fits that width exactly:

Now, from using this image as a background, and employing the following options:

… I’m now expecting the orange line to run through the middle of my repeater for however tall my repeater is. Unfortunately, I get weird results, so this is where I need your help.

If I use the settings above, not only does the background not tile; it’s completely gone. See below:

If I instead choose “scale to fit”, then I’d expect the BG to fit into the width perfectly, and only stretch vertically, but that’s not the case at all. These are my settings:

And this is the mind-boggling result:

The last option is “original size”

Strangely, this is actually the closest to what I’m going for:

Only I wished it would either stretch or repeat over the entire vertical space.

Please help!