Auto-trace in After Effects does not work properly
Hello,
The problem is auto-trace does not creating a mask for the whole size of my video, just a part of it.
I imported my video, used keylight 1.2
Created a rectangular mask, to remove walls out of both sides of green screen.
Then I tried to use auto-trace, but it traced only a part of it (I suppose rectangular)
P.s.
I checked the beginning of the video, it traced ok.
But it is true for only one frame
Help please, what I am doing wrong?

Here is my options for tracing (sorry, it`s in Russian)
I am using Windows 10 x64, intel core i5-3330 CPU 3Ghz, RAM 6 Gb , nvidia Geforce GT 640
