This is probably due to iOS texture size restriction. When a single canvas or an image is bigger than a certain size, the browser stops to load it. And our TMXLayer cache the entire layer in a canvas, so its size equals to the tile map size. Briefly that’s the reason.
Unfortunately we can’t walk through the problem except make tile map smaller with the current design of TMXLayer. But we are looking forward to refactor it very soon.
Sorry for the inconvenience