Thanks Casper for this and your other answers.
Sorry I wasn't clear before. What I meant was that on some pages I have the weave being bigger than the screen and bigger than the furthest tool plus the page padding. So bigger than it should be according to how it should work. It's only by about 100 pixels so not really a great deal.
Now I have solved the problem. There was something odd about one of the images. Looking with photo app (windows 10) it looked to be in portrait orientation, but when imported it was landscape. So I rotated it. It was near the edge of the weave and the extent of the weave appeared to be where it was when the image was unrotated.
Anyway it doesn't matter now as I have corrected the image, although I am not sure if there is some bug?