Another Reason
If there really is tension among the fab four, it must not have helped that Queen Elizabeth picked Harry to be the Youth Ambassador to the Commonwealth. Some say that being passed on for it hurt William.
Confirmation
Royal fanatics tend to push back the thought of conflict and say that the press is only making things up. However, the two couples once got asked if they have disagreements. An awkward silence ensued, and William broke it by saying, “Oh yes.”