Button events not firing unless held down for a while

Hi,
I am pretty new to Unity however I managed to run across certain tutorials etc. I am software engineer so I am familiar with coding, especially c#. Problem is with Unity Application for iOS.

I inherited certain project that I have to fix couple of bugs I fixed majority of them however I have been ignoring certain issue that I had from day one, and unfortunately my research has failed. Basically if I run application using Play button inside the Unity everything works fine and as expected. However If i Build and Run the same project on an actual physical device(iPad, 2 different one to be precise, which leads me to thinking issue would occur on all devices) . For some reason Buttons are not responding unless I hold them down for a while. Interesting part is that Application contains certain scroll views and those work fine. Application respond immediately as soon as you try to scroll through certain items. Interestingly if buttons have animation on touch included that Animation is firing as soon as i tap the button. It seems like its an actual events that are not firing correctly. I created a new button for testing just to see if maybe something went wrong when I was migrating project to newer version of Unity, but new buttons works the same way as old. If someone could lead me on what the problem is, or where possibly I should be looking into to fix it I would much appreciate it.

Thank you

Woj,

public void ButtonStartPressed(){
ShowPage (“MainMenu”);
}

[124888-screen-shot-2018-09-20-at-112310.png|124888]

As requested this is one of the buttons.

Well I Managed to figure it out. For those of you who come across similar issue after migrating your iOS project to newer Unity Version, this might be interesting information.
It looks like new Unity update breaks the OnClick() event interceptors. So if you application consists Buttons that only relay on Button(script) you will have to add to that button new component. Previously OnClick functionality was able to intercept events automatically, this is not the case anymore. You need to add UI Selectable Extension (Script). There you have 3 options to choose from. OnButtonPress(), OnButtonHeld() and OnButtonRelease(). I guess it doesnt need explanation which button is used for what purpose. In my case i had to add the same script I used before to OnButtonPress(). Everything works as expected. Thx for the answers and your time @KittenSnipes and @JVene.