Strange touch/press area behavior

i don't know if it's a bug or not, but either way it's a strange behavior in KLWP .

I'll try to explain, and attach some screenshots.
I am testing simple navigation with 3 buttons, square, star and circle. Pressing one of those buttons opens corresponding object(square in this case).
Anyway animation part works fine, no problem there.

The problem is in button area that reacts on press.My buttons are in this order:

- Main Stack with horizontal-center orientation (Buttons Group)
- Inside Main Stack, there are 3 stacks. Each stack contains Icon and Text, which represents a Button.

I have applied Touch function to each of those 3 Buttons(stacks). Behavior of the First and third buttons (square and circle in this case),is normal,
the problem is that second(middle) button which is Star reacts on pressing not only on button itself but all-around. On attached screenshot, i painted yellow area that reacts on pressing Star button.

I've tried to rearrange buttons(stacks), but this behavior always applies to middle one.

It looks like, Touch function is applied to whole Main Stack, and not to Star Button only, because, if i add more padding, bigger area reacts on touch.

Just to add, I made a copy of Main Stack, and positioned it at bottom, no strange behavior, but upper one still has problem. Also tried removing Status bar in Nova setting, but problem remains.