Hey there. If you know that the material is of type PBRMaterial then you can cast it to that like below for example. It’s not a bug thou, just one of the joys of using TypeScript.
(this.ringText.material as PBRMaterial).albedoTexture = textureGround;
Hmm if you can narrow it down to a more specific question/issue and ideally make a small TypeScript playground for it then I’m happy to try to help, but otherwise I’m not sure how to.