I can’t reproduce this with the following live example: Edit fiddle - JSFiddle - Code Playground
It just reports the expected warning: THREE.MeshStandardMaterial: ‘specularMap’ is not a property of this material.
Using a specular component when the lighting model already uses metalness is redundant (see Specular color map? · Issue #7290 · mrdoob/three.js · GitHub). Also see: