I’m wondering, Ariel, if Jonathan’s question from April on the Mastermatic comment section was ever resolved? I think I’m seeing the same thing he encountered—linked frames shrinking to zero size after running Mastermatic 2.3.3 in InDesign 17.2.
To quote what he wrote (because he explained it so well):
When I’m working on a document that includes anchored objects (either images or text) sometimes the frames that contain the anchored objects will randomly shrink down to the point that they’re microscopically small. In essence, it’s basically like the anchored object completely disappears, except that it’s technically still there just too small to be visible. It seems to be connected to Mastermatic updating the document with the master pages.
I had never seen this problem before running Mastermatic.
There have been several reports of this issue as far as I can tell. The answer seems to be that it is an InDesign bug, meaning that even if you apply the master pages manually in InDesign the issue with the anchored objects occurs.