Texture doesn't change the 3rd time ???

Hello.

Most likely, the problem is somewhere on your side, and most likely at some point you are creating a second panorama.
In your video (time 1:40), you can see that when you open the panorama, the slider in the hierarchy changes.
But, unfortunately, I have not seen your visual scripts, and I can’t say for sure what and where you are doing wrong.

Hello,

I have a very similar problem.
I use the CubeFacesPanoRenderer and I change the renderer's textures at runtime using :

CubeFacesPanoRenderer.SetSide(int index, Texture2D texture)

But if I try to change it 3 times the textures won't change anymore.

I did a bit of research in the code and it seems the problem comes from the hasMesh field in PanoRenderer.
The field is reset to false in OnEnable() but is never set to true after that.
To hide and show the panorama I activate or deactivate the Panorama gameobject.

It's worth mentioning that if I try to use the CreateMesh() or UpdateMesh() function it causes an infinite loop.

EDIT :
If I comment line 265 in file PanoRenderer.cs the problem disappears :

protected void OnEnable()
{
    _pano = GetComponent<Pano>();
    hasMesh = false; // Line 265
}

But I'm not sure this is a correct solution.