Passengers with sailings booked on Royal Caribbean International's Allure of the Seas are currently receiving emails from the line saying that their itinerary has been changed due to speed restriction.
The cruise company has not indicated the nature of the issue precisely. Based on emails sent to travelers, it appears the changes predominantly affect Eastern Caribbean itineraries, with St Thomas being replaced with San Juan.
Propulsion problems among cruise ships are not uncommon and result in slower speeds until the issue is addressed in port. Line's Anthem of the Seas had the similar issue in March, Liberty of the Seas a couple of years ago, Freedom of the Seas in 2014, and Allure back in 2013.