WordPress Visual Editor Kitchen Sink disappearing issues.

You know best about your WordPress installation, so you are the right person to solve the issue.
Make a note of every minor changes you made to the WordPress core files, plus those on themes and plugin customization.

The Kitchen Sink Visual Editor is finally back.

What was tried:

• Disable plugins
• Disable themes
• Disable CDN
• Disable editing capabilities
• Enable debug
• Finally reboot your server, lucky if you are running the site via VPS just like this website.

Make a summary of things to try to troubleshoot as mentioned here
https://wordpress.org/support/topic/visual-editor-not-working-after-upgrade-to-40/page/2
I spend 3 days figuring out what the actual issue was and finally there was the solution.
Let me share what I did so far to solve this issue.