Rendering issue in image + textbox exported from InDesign

Hi, when in InDesign CC 2020 I group an image with its caption (a text-frame) the export in EPUB is:

<div class="_idGenObjectLayout-1">
	<div id="_idContainer009" class="_idGenWritingDirection-1">
		<div id="_idContainer007" class="Cornice-di-testo-di-base">
			<p class="didascalia">Pietra di confine con la scritta «Oropa» nel bosco di Fontanelle annesso alla cascina Simonetto sotto la proprietà di Giovanni Battista Garrone nel XVIII secolo. (Archivio Virginia Gozzi Brayda)</p>
		</div>
		<div id="_idContainer008">
			<img class="_idGenObjectAttribute-1" src="image/00.jpg" alt="" />
		</div>
	</div>
</div>

With the following CSS:

#_idContainer007 {
	height:59.53px;
	left:0px;
	overflow:hidden;
	position:relative;
	top:213px;
	width:360.00px;
	z-index:1;
}
#_idContainer009 {
	display:inline-block;
	height:272px;
	position:relative;
	width:360px;
}
#_idContainer008 {
	height:212.60px;
	left:0px;
	position:relative;
	top:-60px;
	width:360.00px;
	z-index:0;
}
img._idGenObjectAttribute-1 {
	height:100.00%;
	min-width:100%;
	width:100.00%;
}
div._idGenObjectLayout-1 {
	text-align:center;
}

The issue is that Thorium cuts part of the caption:

I can send you a test file privately.

[JayPanoz]

Yeah, at first sight their markup + styling for figures got an awful lot worse in CC 2020 – which I thought couldn’t be possible given how bad it already was. I’m guessing the combo of div id + absolute/relative positioning + inline-block may be a lead.

[danielweck]

Closing as not fixable in Thorium. Probably needs details fleshed out in ReadiumCSS https://github.com/readium/readium-css/