I definitely went looking for similar bugs. I found a few, but they didn't seem to be similar to what I was seeing. As far as XS goes, I have some custom XS in there and this was breaking near the point where I start to use it, so I assumed it was my own code causing the problem.

It turned out the issue wasn't XS and my assumption there led me down the wrong rabbit hole quite a ways before I realized my mistake. I updated the post above.