When exporting a PDF of a document with a long chain of headers, all the headers will try to stay on the same page and will run below the bottom of the page, becoming invisible

The headers get a keep-with-next attribute which tries to keep a header and the following paragraph together. Unfortunately, when many headers come one after another, the strength of the rule (always) prevents page breaks between them.

The same things happens for dt elements and {{tr}}s which contain only {{th}}s.