Updated builds.

build/three.cjs

@@ -11489,7 +11489,7 @@ class Mesh extends Object3D {
 
 		}
 
-		this.material = source.material;
+		this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 		this.geometry = source.geometry;
 
 		return this;
@@ -32352,7 +32352,7 @@ class Line extends Object3D {
 
 		super.copy( source, recursive );
 
-		this.material = source.material;
+		this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 		this.geometry = source.geometry;
 
 		return this;
@@ -32673,7 +32673,7 @@ class Points extends Object3D {
 
 		super.copy( source, recursive );
 
-		this.material = source.material;
+		this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 		this.geometry = source.geometry;
 
 		return this;

build/three.js

@@ -11494,7 +11494,7 @@ console.warn( 'Scripts "build/three.js" and "build/three.min.js" are deprecated
 
 			}
 
-			this.material = source.material;
+			this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 			this.geometry = source.geometry;
 
 			return this;
@@ -32357,7 +32357,7 @@ console.warn( 'Scripts "build/three.js" and "build/three.min.js" are deprecated
 
 			super.copy( source, recursive );
 
-			this.material = source.material;
+			this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 			this.geometry = source.geometry;
 
 			return this;
@@ -32678,7 +32678,7 @@ console.warn( 'Scripts "build/three.js" and "build/three.min.js" are deprecated
 
 			super.copy( source, recursive );
 
-			this.material = source.material;
+			this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 			this.geometry = source.geometry;
 
 			return this;

build/three.module.js

@@ -11487,7 +11487,7 @@ class Mesh extends Object3D {
 
 		}
 
-		this.material = source.material;
+		this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 		this.geometry = source.geometry;
 
 		return this;
@@ -32350,7 +32350,7 @@ class Line extends Object3D {
 
 		super.copy( source, recursive );
 
-		this.material = source.material;
+		this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 		this.geometry = source.geometry;
 
 		return this;
@@ -32671,7 +32671,7 @@ class Points extends Object3D {
 
 		super.copy( source, recursive );
 
-		this.material = source.material;
+		this.material = Array.isArray( source.material ) ? source.material.slice() : source.material;
 		this.geometry = source.geometry;
 
 		return this;