So I was deploying one page at a time until one page resulted in the error. Then from the page I was removing components until I've figured out the problem.
Apparently, the html editor
component allows you to save an anchor tag without its closing tag, and everything looks good.
<div>
<a href="asdasd">
</div>
Despite that, after inspecting the element in dev console, the closing tag is in place. So they have some polishing processes for this, but in the metadata it is still missing.
<a target="_blank" href="asdasd"> this. </a>
Nevertheless, this page could not be saved. After fixing the missing closing tag, everything deploys as it should.