Ran into a strange situation.
In html

<div class="image-container">
<figure class="alignoutside">
<img src="an-image.jpg" width="330" height="270" class="dpi300">
<figcaption>A caption</figcaption>
</figure>
</div>

there's a lot of redundant css on this type of codeblock (pulling from several different stylesheets and i'm trying to clean it all up to get to what is needed and only what is needed), but, what seems to be relevant here is this

/*.image-container alignoutside {
display:table;
}*/
figure {
box-sizing: content-box;
width:min-content;
}
.alignoutside {
float: outside;
}
.dpi300 {
-prince-image-resolution: 300dpi;
}

Before commenting the .image-container the images display as expected. After commenting, the images get shrunk down to approximately 32% give or take (I'm not actually measuring them, although some are much smaller) of the explicit dimensions. If I remove the height and width from the image tags, the images go back to their expected size, and the caption wraps as necessary. Is this expected behavior (the way I'm understanding the image-resolution is that it uses the dimensions *or* the stated dpi from stylesheet, not both, potentially scaling twice), or, is it more a weirdness relating to the min-content?

I wasn't able to reproduce anything strange from the snippets you provided. Perhaps you could post a full test case and the produced PDF, if it is not working how you expect.