Fol. 83v has a heading in the left margin, but it is rendering center - before I make an issue in Nick's repo, @njr2128 and @thuchacz, is this markup fixable?
The markup is fine—there is a position attribute in the header. This is part of the "known" issue by which, at some point in late January, Nick's code lost the ability (which it firmly had, a few months ago) to render headers in the margin.