I am having the same problem using Radial fill. Application runs fine on the editor but crashes in the mobile build.

Well scratch that. I was tired and mixing up the input held vs input down events. The coroutine starts once.

Ended up solving this simply by increasing the size of the canvas that contains the radial selection. I'm still not sure why this works exactly. Fix found here:

https://issuetracker.unity3d.com/issues/ui-android-slash-ios-changing-image-fillamount-causes-freeze-on-small-world-space-canvas-on-mobile

Can't see the reproduction project. But I encountered exactly this bug with the SelectionRadial script from the free Unity VR Samples pack. In case anyone else is looking for a solution to this here is some info.

There is a bug in the script, as long as the mouse input (or touch pad or what have you) is held down it keeps spawning infinite coroutines until the radial is filled or disabled. For some reason this worked in 5.3 but it causes performances issues in 5.4 which really should be expected.

A fix: I used an extra private bool m_StartFill initialized to true.

private IEnumerator FillSelectionRadial(){
m_StartFill = false;
...
}

private void HandleDown(){
if (m_SelectionRadialActive && m_StartFill){ //this prevents more coroutines from spawning
...
}
}

private void HandleUp(){
m_StartFIll = true;
...
}

And for good measure you probably want to stop the fill coroutine when the radial is hidden.

public void Hide(){
if(m_SelectionFillRoutine != null){
StopCoroutine(m_SelectionFillRoutine);
...
}