TouchTracking cannot scroll vertically?

[mcguu2020]

I am using Xamarin.Forms Shell and TouchTracking.Forms

I can get touch location from TouchActionEventArgs when I touch horizontally

but when I touch the screen vertically the Location.Y will become the max point soon while I scroll and never change then.

that 's why?

here is the Y position

69.74557
69.74557
69.74557
69.74557
69.74557
69.74557
70.40048
75.99146
400.6303

it will become 400.6303 when I touch down the screen and do not change while then.