EasyMonkeyDevice touch sometimes tap on wrong coordinates

My program is trying to establish a VPN connection, thus, I get the Android message about "Connection Request - your software wants to setup a VPN connection ... Only accept if you trust the source". From uiautomationviewer I saw the ID is id/button1. So, I've used this

easy_device.touch(By.id('id/button1'), MonkeyDevice.DOWN_AND_UP)

The OK button according to uiautomationviewer is at [810,1162][978,1288], But monkeyrunner taps on X=866, Y=709

170725 15:43:58.893:I [main] [com.android.chimpchat.ChimpManager] Monkey Command: tap 866 709.

What am I doing wrong?