Changes to WP pages are wiped out each night

I am helping a company with their WordPress site: youradminpartners.com

Each day, I edit content in the pages or php files in the editor. You can see them on every PC in several locations. It happens to everyone in the company, at the office and at home. Then, each night, those changes are undone and the page reverts to an older version — prior to those changes. I put the changes in again and they are saved the second time.

It has happened every day for 2 weeks. I saw it last night as I worked on page content in the editor. I tested it (checking to see that the changes showed on the site on a few PCs) and everything looked fine. At 10:45pm (EST), the page reverted back to the previous saved version.

How do I stop this from happening?