fix: build metaData from a deep clone of the template

app/config.js

@@ -1,5 +1,6 @@
 import fs from 'fs';
 import path from 'path';
+import cloneDeep from 'lodash/cloneDeep';
 import defaultConfig from './configurations/config.default';
 import configMerger from './util/configMerger';
 import { boundWithMinimumAreaSimple } from './util/geo-utils';
@@ -8,6 +9,8 @@ const configs = {}; // cache merged configs for speed
 const themeMap = {};
 // Look up paths for various asset files
 const appRoot = `${process.cwd()}/`;
+// eslint-disable-next-line global-require
+const metaDataTemplate = require('./ssrmeta.json');
 
 if (defaultConfig.themeMap) {
   Object.keys(defaultConfig.themeMap).forEach(theme => {
@@ -42,8 +45,8 @@ function addMetaData(config) {
     }
   }
   // read metadata template and modify it to match image assets generated by favicons-webpack-plugin
-  // eslint-disable-next-line global-require, import/no-unresolved, no-param-reassign
-  config.metaData = require('./ssrmeta.json');
+  // eslint-disable-next-line no-param-reassign
+  config.metaData = cloneDeep(metaDataTemplate);
   config.metaData.link.forEach(link => {
     // eslint-disable-next-line no-param-reassign
     link.href = link.href.replace('<themehash>', manifestName);