Erm, is this #9638?

Oh yes! But are you referencing a closed bug report?

Yes. Has the reproducibility situation changed since then?

Don't think so. I can repro, for example, when document.width is 2021.

I think this is a positioning bug caused only by the rounding of half pixels—I can see a shifting tooltip at other odd browser widths as well. I imagine what needs to happen is that the position needs to be rounded up or down to the nearest whole pixel.

ugh this is because we use jquery.offset() to position our tooltips… which doesn't round numbers.