I doubt it would have been anything to do with the children. If something minor happened nannies would have dealt with it. If something major happened they'd have announced it.
Which means it has to be something to do with William himself, either physical or mental.
I am starting to wonder if it's been a sort of MH breakdown, the realisation his Godfather is away, his DGPs are gone, his Dad and (Auntie) Sarah both have cancer.
He doesnt have his brother beside him. And that trust is gone. He must be under an incredible amount of pressure and nobody to really have his back.
The Queen for years had the rock solid support of Philip, her mother, her sister, her cousins, and Anne, Charles, Edward and Andrew 😬