Try it like so.
line 213:
let linePosCount = 200; // max value
// frame center line (A)
gCenterLineA = new THREE.BufferGeometry( );
gCenterLineA.positions = new Float32Array( linePosCount * 3 );
gCenterLineA.setAttribute( 'position', new THREE.BufferAttribute( gCenterLineA.positions, 3 ) );
centerLineA = new THREE.Line( gCenterLineA, new THREE.LineBasicMaterial( { color: 0xffffff, side: THREE.DoubleSide } ) );
sceneA.add( centerLineA );
gCenterLineA.setDrawRange ( 0, markerCountL + 1 );