With a specific combination of resource packs (likely a PBR one and another that alters the banner/banner pattern textures) banners will display a random banner pattern of their base colour while the rest of the banner remains black. I have tested this with both Kelly's RTX https://mcpedl.com/kellys-minecraft-vanilla-rtx-conversion-pack/ and my own PBR resource pack.

Steps to Reproduce:

1. Open a world with Ray Tracing on and with the two resource packs linked below applied to global resources.
2. Place and view a banner of any colour.

Observed Results:

The banners display a Snout banner pattern in the colour of their base colour, and the rest of the banner is completely black.

Expected Results:

The banners should retain the same functionality they had before applying the second non-PBR resource pack, as in displaying their base colour without any banner pattern (as there are none applied).

Global Resources:

Defined PBR: https://www.mediafire.com/file/xnr66e9foxfcoi5/Defined_PBR_v1.1.4.mcpack/file

MultiPixel: https://www.mediafire.com/file/g890rxv9yg4epad/MultiPixel_Bedrock_1.17_rv1.mcpack/file