I had almost same issue. You ca try target.frontMostApp().mainWindow().scrollViews()[0].scrollViews()[0].tapWithOptions({x: 27.0, y: 949.0}, {duration:3});
If you see the documentation, tapOffset is not the exact x and y positions. It is just relatives values between 0 and 1. You have to calculate these relative values according to x, y positions.