UI flicker / Icons displaced in build (Video)

Hello gents,

I've had a bit of a problem recently and the only relevant google search associated with my problem was to downgrade Unity version :/ Perhaps you've encountered this problem before and might give me a hand !

5 seconds video to explain my issue

https://www.youtube.com/watch?v=TNCMcPuQFRI&feature=youtu.be

No error in editor. In build version, when popping up the Tooltip (pointer enter 1s on spell icon), the UI flickers or/and spells icons gets displaced for 1 frame, ~= 10% chance of happening every tooltip call (See 5s Video above).

Timer for ToolTip (timer = 0 when PointerEnter of button is called, timer = -1 when ToolTipOn/PointerExit called):

         float time = -1;
         UIToolBox uitb;
     
         public void Awake()
         {
             uitb = FindObjectOfType<UIToolBox>();
         }
         public void Update()
         {
             if (time >= 0)
             {
                 time += Time.deltaTime;
                 if (time > 1)
                 {
                     uitb.ToolTipOn(spell.desc, buttonpos);
                     time = -1;
                 }
             }
          } 

Tooltip showing up = RawImage.enabled. (tried with go.SetActive, same problem)

Tooltip content = 1 RawImage, 1 Text All icons/base UI are RawImage. ( tried before with Image, same problem)

using Unity 2020.1.7f1 (Latest)

My canvas Tree:

Ask for additional info if needed

Thank you!