Problem: When you let your Drupal 8.7 website cache content and assets for a long time without clearing the cache, keep in mind that sometimes when you attempt to clear the cache, the website might throw an error. - When this happens, don't panic instead see solution below: Error: The website encountered an error, please try again later. Solution: Keep on clearing the cache until you see the "Cache Cleared Successfully" on your dashboard notification section. There is a chance that Drupal 8.7 core library is only clearing the cache 1 week going back, this is, of course, depends on the setting you have defined on the same page you are clearing the cache. - Keep in mind that clearing the Cache unnecessary can cost your website some performance hit. This should be done only when it is absolutely necessary like when deploying new modules.