I have written a simple application and deployed it on Sony Xperia Z and Galaxy Prime devices. On both it's really very hard (I've got to click many times before it reacts) to:

put focus on a TextInput
select a ToggleButton
click a Button
etc.

The same time a ScrollView (that is the container for the mentioned widgets) works perfectly smooth. And when run on desktop then it's alright.
I use kivy 1.9.1, python 2.7, build on Ubuntu 16 using buildozer. Don't know what else could I say... (Let me know, please)
Have you experienced such an issue?
You should update to kivy 1.9.2-dev, the problem is fixed there. In buildozer.spec file, write requirement kivy==master.
Kivy - hard to select Widgets