OK, two cases as mentioned in my OP.
Case one:
432 page book, b/w only. 17 chapters plus front- and backmatter. Production proceeds smoothly through two rounds of proof. On the final pass, chapter 10 dies. It happens at the beginning of an ordinary paragraph, but CC won't let me touch it without deleting text from there to end of chapter and crashing. No special fonts (used or reported) or characters, standard paragraph and character styling. Solution: exported the offending paragraph to text, deleted the spread on which the event took place, reinserted new blank pages and reimported text. Opinion from Adobe tech support? Nada.
Case two:
256 page two-color (black + spot) book. Fairly elaborate design. Done as a single file. At about page 150 file crashed. Same fonts, styles (paragraph, character, object), used throughout. From that point on I could not recover the file by writing out to idml (crash), writing out to InCopy (crash) moving pages (crash), deleting and reimporting content (crash on delete), deleting and reinserting pages (crash). After some time with tech support (chat and phone), I was invited to send the file to for Adobe analysis. I was told I could expect information in 24-48 hours. At about the 60 hour mark, I inquired using my assigned case number. I was asked (after being screened for application type) if this was an InDesign inquiry. After referencing my case number, the support person said she would look into it and get back to me. Two days later, I got an e-mail asking if my issue had been resolved. Mind you I had heard nothing in the meantime.
So, while all that tech support is not happening I am trying all the usuals and nothing works. And I now have a document that crashes whenever I do any of the following: attempt a search/replace or attempt to find a font, change any style or swatch in any way, attempt to use the table of contents feature. And along the way, text starts to disappear from pages. It's there, but I cannot see it (verified by writing pdf files). Oh and mystery fonts begin to appear (fonts that I don't own or have on my system).
I think Adobe should offer more for subscribers!!