Button highlight not intended on Android and iOS

Hi,
So you can understand my bug i will explain what my scene looks like.
I have two full white screen with a button on each.
The two buttons have the exact same position.
Clicking on the button we see, will disable the white screen containing this button i click on. This will reveal the 2nd white screen with the 2nd button on it.
Clicking on this 2nd button will enable the first white screen, revealing the first button again.

My issue is that when I tap on the first button, the second button will appear normally, but a few moment after will be highlighted.

To prevent this I tried to launch a coroutine when i tap on the first button so the second button will be enable 5 seconds after the first button is pressed. After the five seconds the button appeared normally but like before, just a few moment after, the button is highlighted.

Can somebody help me with this ?