With a little bit of diagnosis, it turns out that https://github.com/xwiki/xwiki-rendering/blob/5d30ae5796bbb133ac3a8ddb7c24886930fc6dd9/xwiki-rendering-syntaxes/xwiki-rendering-syntax-xwiki20/src/main/java/org/xwiki/rendering/internal/renderer/xwiki20/XWikiSyntaxChainingRenderer.java#L350C9-L350C9 will throw an NPE because, in these cases,

It probably comes from having content directly in the <table> element which does not make much sense from XHTML point of view, so the parser does not expect it.