Disappearing text boxes in Pages 7.1
I'm working on a large picture book with some text and captions. Sometimes, inexplicably, when I click on a text box and drag it to a different location, the text within just disappears. Weirdly, this doesn't happen in the upper two thirds of the page (I'm in Page Layout mode) - only in the bottom one third of the page. When I set up a new document from scratch and paste in the offending text box, this doesn't happen - I can drag it around anywhere on the page without problem.
The document has 100 pages, so maybe it's something to do with that? It's as if there is some sort of force field in the bottom two thirds of the page!
Your help appreciated!
MacBook Pro with Retina display, macOS High Sierra (10.13.5)