Is this issue still being worked on ? It says fixed and yet it doesn't seem to be.

Well, that one's a showstopper.
Back to 2018.4 then...

reoccur problem in 2019.3.0a4.

Allow Switch off + Active ON/OFF...
Selection is move to Last TAB...

reoccur problem in 2019.3.0a4.

Just to save to time testing: Still not fixed in Unity 2019.1.5 :/

This was stopping me from updating to 2019 so I created this small helper MonoBehaviour script that resolved the "forgetting" issue.

I added to every gameobject that has a ToggleGroup. It should help stop "forgetting" which toggle was selected when it becomes enabled again.
Hope this helps others.

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ToggleGroupHelper.cs
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using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class ToggleGroupHelper : MonoBehaviour
{
private Toggle rememberMe;

private void OnEnable()
{
if (rememberMe != null)
{
rememberMe.isOn = true;
rememberMe.onValueChanged.Invoke(true);
}
}

private void OnDisable()
{
List<Toggle> active = new List<Toggle>(this.GetComponentsInChildren<Toggle>(true));
this.rememberMe = active.Find(t => t.isOn);
}
}

Doesn't seem to be fixed in 2019.1.4f. I still get the same behavior. Very frustrating...

Would really appreciate this being fixed in 2019.2 instead of .3

For anybody in a rush for a temporary solution this might help. Here is a version of ToggleGroup based on Unity's source on GitHub.... My change is: it searches for Toggle components in children at Start() and doesn't set (or rely on) the Group reference in each Toggle. Which means when a Toggle is disabled it DOESN"T call the usual group code that does the unwanted stuff. No guarantees .... it might work for you ...great. It is named differently so you would have to replace the standard ToggleGroup with it.

using System;
using System.Linq;
using System.Collections.Generic;
using UnityEngine.EventSystems;

namespace UnityEngine.UI
{
//x[AddComponentMenu("UI/Toggle Group", 32)]
[DisallowMultipleComponent]
public class ToggleGroupPJJ : UIBehaviour
{
[SerializeField] private bool m_AllowSwitchOff = false;
public bool allowSwitchOff { get { return m_AllowSwitchOff; } set { m_AllowSwitchOff = value; } }

private List<Toggle> m_Toggles; //x = new List<Toggle>();

protected ToggleGroupPJJ()
{}

private void f_validateToggleIsInGroup(Toggle toggle)
{
if (toggle == null || !m_Toggles.Contains(toggle))
throw new ArgumentException(string.Format("Toggle {0} is not part of ToggleGroup {1}", new object[] {toggle, this}));
}

public void NotifyToggleOn(Toggle toggle)
{
f_initialize();
f_validateToggleIsInGroup(toggle);

// disable all toggles in the group
for (var i = 0; i < m_Toggles.Count; i++)
{
if (m_Toggles[i] == toggle)
continue;

m_Toggles[i].isOn = false;
}
}

public void UnregisterToggle(Toggle toggle)
{
if (m_Toggles.Contains(toggle))
m_Toggles.Remove(toggle);
}

public void RegisterToggle(Toggle toggle)
{
if (!m_Toggles.Contains(toggle))
m_Toggles.Add(toggle);
}

public bool AnyTogglesOn()
{
f_initialize();
return m_Toggles.Find(x => x.isOn) != null;
}

public IEnumerable<Toggle> ActiveToggles()
{
f_initialize();
return m_Toggles.Where(x => x.isOn);
}

public List<Toggle> AllToggles()
{
f_initialize();
return m_Toggles;
}

public Toggle FirstActiveToggles()
{
f_initialize();
return m_Toggles.Where(x => x.isOn).FirstOrDefault();
}

public void SetAllTogglesOff()
{
f_initialize();
bool oldAllowSwitchOff = m_AllowSwitchOff;
m_AllowSwitchOff = true;

for (var i = 0; i < m_Toggles.Count; i++)
m_Toggles[i].isOn = false;

m_AllowSwitchOff = oldAllowSwitchOff;
}

List<bool> m_WhatChanged;

public void onToggle(bool b)
{
int ind = 0;
if (b == true)
{
int changedInd = -1;
ind = 0;
foreach( var tog in m_Toggles )
{
if (tog.isOn != m_WhatChanged[ind])
changedInd = ind;
ind++;
}
if( changedInd != -1 )
{
bool priorDisableState = UIMapping.m_DiableUICallback;
UIMapping.m_DiableUICallback = true;
ind = 0;
foreach( var tog in m_Toggles )
{
if (tog.isOn && ind != changedInd )
{
tog.isOn = false;
}
m_WhatChanged[ind] = tog.isOn;
ind++;
}
UIMapping.m_DiableUICallback = priorDisableState;

}

}
ind = 0;
foreach (var tog in m_Toggles)
{
m_WhatChanged[ind] = tog.isOn;
ind++;
}

}

void f_initialize()
{
if( m_Toggles==null )
{
m_Toggles = transform.GetComponentsInChildren<Toggle>().ToList();
m_WhatChanged = new List<bool>();
foreach( var tog in m_Toggles )
{
tog.onValueChanged.AddListener(onToggle);
m_WhatChanged.Add(tog.isOn);
}
}
}
public void ReInitialize()
{
m_Toggles = null;
f_initialize();
}
//!? Hack if dynamically created toogles
//!? aren't created by 'Start' time then they won't be found
protected override void Start()
{
base.Start();
f_initialize();

}
}
}

The same but slightly. different Additionally It was inconvenient to get a 'UI Toggle Event' when disabling a panel with a toggle group. I don't regard disabling a panel with groups the same as clicking a toggle.