Indesign CC ligatures turning on randomly

Question

I'm having a problem with ligatures appearing uninvited in my Indesign CC documents. I'm an artworker and this is making me very nervous when sending out files to print. Quitting/restarting Indesign will generally resolve the problem. I haven't been able to isolate a situation that triggers this and I've experimented using different fonts, font types, etc. Sometimes I can open the same document 5 times with the ligatures appearing and on the sixth time it fixes itself.
I've trashed preferences which hasn't helped. I have turned off ligatures in the character panel with all documents closed. I've checked the paragraph styles of the documents that are exhibiting the problem and turned off ligatures in character panel, but after saving and closing the document, they reappear when I reopen. Quitting Indesign is the only way to (temporarily) resolve the issue.
I haven't run the latest update, but this problem has occurred across the last 2 or 3 Indesign CC updates. I'm using Universal Type Client 4.0.1 on OSX 10.9.4. Other people in my studio running effectively the same hardware/software are also experiencing the problem.
Any assistance most appreciated.
Adam

Answer 1

Hi Rick,
I've sent example files to Adobe and so they are now fully aware of the issue and can hopefully resolve it.
I had a file yesterday that was exhibiting the problem and some of the tests I did threw up some worrying behaviour. Duplicating the problem file in the same folder and opening it not only turned off the ligatures, but it also turned off the ligatures in the original problem file. I then closed the duplicate and the ligatures turned back on.
I also changed the font of the character pairs that were creating the ligature, which fixed the problem, even if it was just changing to a different weight of the same typeface. I then applied the paragraph style in use on the problem characters to a paragraph that used the same typeface and weight in another place in the document - that introduced the problem to those characters too. Problem is the ligature settings in both para styles are identical.
The other problem was when I stripped out 11 of the 12 pages from the document to send it to Adobe, including all of the HR images, the file size didn't change from 64 mb, even though the document was 1 page with 1 image in it and a few paragraphs of type.
Bottom line - if you quit Indesign and restart, I've found it will generally resolve the problem.
Good luck - hopefully you don't send a file out to be printed without noticing the ligatures have turned on.