The first time it happened was in July, but at the time we assumed it
was a mistake of ours.More recently we've noticed it intermittently over
the last 3 weeks.It became really obvious last Monday 6 November, as we
were updating all of the collections in the project, and it's been
happening to around a quarter of them over the last week.We've been
going through and fixing them over the last couple of days. I'll update
when we find the next collection that is missing articles.