I have asked some friends who have cruised and so has my wife and no one has experienced two instances back to back where a cruise line has changed itinerary's. Look yout your case...39 cruises, two port changes and no itineray change...my case 3 NCL cruises, 2 cruises where ports were eliminated or substituted and an extra day added at sea. From what I understand from another group NCL has a history of this.
I read the fine print and was well aware if the "change without notice' caveat. But heard it is rarely utilized.
thanks for your answer
we cancelled and went with RCCL