In progress issues article order

Per https://specifications.silverchair.com/xsd/1/38/XMLSpecJournProc.html#defaulttocordering the sites will order articles on the issue table of contents (TOC) by start page (or elocation-id), grouped first by article type or category, by default. Whether the issue TOC groups articles by article type or by category is configured during your site’s build.

In our case, the articles are grouped into TOC headings and then ordered by elocation-id within those headings (which stops headings from repeating by putting them all into one group).
The order of the headings themselves is still largely elocation-id so the heading of the article with the lowest elocation-id becomes the first heading and then all articles with the same heading get grouped under it then it looks for the next heading of the next lowest elocation-id available and grabs all articles with it etc.