Related Items in single item layout just disappeared!

Related Items in single item layout just disappeared!

I’ve been building a shop with list layout -> single page layout -> cart … regular sort of stuff.
Yesterday I had a few last items to update in one of my categories - pricing and Related Items.
After the update to those two items I checked out each product and was shocked to see only four black rectangles where the products should have been. (The boxes are cards in secondary style).
I thought this might be only these two products, but it happens with all 140+ products. 
Has anyone had this happen recently?
I checked the demo for DjCatalog2 and nothing shows in their Child Items or Reviews either.
is this a result of a problem in the most recent DJ-Cat2 update a few days back?
I’ll be uploading my site this weekend and in the interim I’ve just left the black rectangles there with a note in the header saying “coming soon”
I hope this is an easy fix as this would mean a minimum of 600 related items to input all told. I have input them separately for each product as doing so randomly would cause all sorts of issues - I think. 3 different sports - completely unrelated by products.