I m willing to check 2 things :
1) Does a Square appears- for you too - on top of the button while it is pressed.
2) Does anyone knows how to remove this square effect ? - if it is even posible...
You will need to build the APK. The problem only occurs on the device, not on the IDE testing mode.
Stack does not do anything but display a shadow and remove a shadow when the button is pressed.
file to test :
