Custom Fields keep disappearing.

I found it confusing when I first started using Custom Fields, so I’ll share what I learned in case it is your problem: you must create/update each Custom Field using the button(s) beside it. Using the Update button for the Page WILL NOT create or update custom fields.

In fact, Custom Fields must be created/updated one at a time. Pushing Update for one Custom Field will lose the changes to another Custom Field, if you haven’t hit Update for it.