Sstrhsrtj

I'm making a book with tufte-book, and having a strange issue where, when I put a figure on a verso, there's extra space between the figure and the subsequent text. It doesn't happen on a recto, and the space isn't there before the caption:

I'm not good at tikz or anything like that, so my MWE's image is a jpg I have:

%! TEX program=xelatex



documentclass[

  symmetric,

  justified,

  sfsidenotes,

  marginals=raggedright

]{tufte-book}



% Page dimensions (crown quarto)

geometry{

  paperwidth=7.44in,

  paperheight=9.68in,

  width=4.0in,

  top=1in,

  bottom=0.75in,

  headsep=0.25in,

  right=2.5in,

  marginparsep=0.25in,

  marginparwidth=1.625in

}

% Before I did the following, the gap was larger but still asymmetrical:

setlength{textfloatsep}{0em}



usepackage{lipsum}



usepackage{graphicx}

graphicspath{{photos/}}



begin{document}



chapter{Introduction}



Let's start from scratch, shall we?



lipsum[1-4]



Here are some words I put here myself to make sure there's no paragraph break

before the figure.

begin{figure*}[t]

  includegraphics[width=linewidth]{portrait1905.jpg}

  caption{Here's a misaligned caption. I'm going to make it longer so

  we can see the effect of multiple lines, although that's not strictly

  relevant to the question. It just makes things clearer.}

  label{fig:four-gen}

end{figure*}

And here are some words that come after the figure.



lipsum[9]

begin{figure*}[t]

  includegraphics[width=linewidth]{portrait1905.jpg}

  caption{Here's another, just for testing purposes. You gotta have QC.}

  label{fig:four-gen-again}

end{figure*}



Okay, but now I gotta figure out whether this space shows up on rectos or

only versos. So I'm gonna put enough text here to make the next picture show

up on a verso.



lipsum[10]



end{document}

This behavior seems to show up consistently on versos and not on rectos, with this page geometry. (On the class's default page geometry, the space is more or less equal on either side of the spread, but it's even more space than on the verso here, and misaligned with the caption in any case.)

I'm guessing this is a bug in the class, but whether or not it is, how can I work around it so that the caption and the text are aligned with each other? It seems like there's some ...length value I should be able to set to 0, but I can't figure out what it would be.