1. If you’re using a child theme, switch to the parent. 2. If you aren’t using a child theme but have modified the parent, switch to a default theme like Twenty Sixteen. 3. If you have a caching plugin, clear the cache. 4. Install https://wordpress.org/plugins/server-ip-memory-usage/, check the footer in the WP admin and check your PHP memory usage, what percentage is it at? 5. You indeed reinstall Page Builder and Widgets Bundle without losing content.