Unable to modify custom shader's properties in scripts' update?

I’ve managed to set up my shader’s SoftMaskable version. But now I can’t change the shader’s properties at runtime.

Shader "Hidden/Custom/UI/Grayscale (SoftMaskable)"
{
	Properties
	{
		[PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
		_Color ("Tint", Color) = (1,1,1,1)
		
		_StencilComp ("Stencil Comparison", Float) = 8
		_Stencil ("Stencil ID", Float) = 0
		_StencilOp ("Stencil Operation", Float) = 0
		_StencilWriteMask ("Stencil Write Mask", Float) = 255
		_StencilReadMask ("Stencil Read Mask", Float) = 255

		_EffectAmount ("Effect Amount", Range (0, 1)) = 1.0
		_BrightnessAmount ("Brightness Amount", Range(0.0, 3)) = 1.0

		_ColorMask ("Color Mask", Float) = 15
	}
        ...

And this is how I set properties in Update (for a short period of time):

LevelImage.material.SetFloat("_EffectAmount", amount);

If I click on the Material in the object’s Renderer itself, it shows the correct effect amount, but under the object, it displays the Hidden Soft Maskable material, with unchangeable default properties.

How could I fix this?

Thanks in advance! 😃

[udvaritibor]

@mob-sakai Thanks, yes, it’s only null at the first frame. 😃 (In the last (now deleted) comment I said that it’s constantly null, but it was null only due to an issue on my side)

[udvaritibor]

@mob-sakai For some reason CanvasRenderer.GetMaterial() returns null :\