I'm ALWAYS suspicious of Suitcase, but it's more likely to be something like cross-references, conditional text, or even keep options being checked.
The document has several hyperlinks that are eventually supposed to be what they are in a digital version of the publication, but obviously not in print. Is InDesign checking those hyperlinks every 7 seconds? They imported with the text, so they were set up by writers and editors outside of InDesign, probably in Word.
I've not seen this "interruption" happen in other projects with hyperlinks that I set up whilst in InDesign.
Before I go and delete all those hyperlinks (because unfortunately I will need them later), could this be the cause of the problem?
I would not think hyperlinks to an external URL would cause this, but I don't use them in my work.
On the offhand chance it was the problem, I deleted all the hyperlinks. I then closed the document and quit InDesign. I re-started InDesign and tried to open the document and got the spinning beachball. I let it sit for a while, but when it looked like it was just locked up, I force quit. I re-started InDesign again, and it rescued the document and, low and behold... the "interruption" is gone.
It gets weirder... everything goes along just fine, until I try to import another text document (.docx) that contains hyperlinks. Then the "interruptions" begin again... and continue even after I've deleted the text box. I have to quit InDesign and re-start. I can open the text document in Text Edit and re-save it, and then the text imports into my InDesign document without issue.
Anyone have any ideas what's happening?