UIbutton not responding consistently to touch event

I placed my UI button inside stack view of storyboard in UIKit App. and I enabled user interaction to both stack view and button. My button width and height are 20,20. I am using this UIbutton for checkbox sometimes it is responsive and sometimes I have to click multiple times. I tried increasing the size of the box but no luck.when I use tip of my nail it works and if I use my entire finger it won't work. I guess when my finger touches both stackview and button it won't work