I’ve done some research to this, and I found some problems related to my but I couldn’t solve.
I’m using WordPress 4.0, ACF 4.3.9 and Woocommerce 2.2.6. I’ve disabled all other plugins but this 2 but didn’t solved my problem. Not using WPEngine.
My problem is that I can’t edit the custom fields I created. I’ve a product that has some custom fields, I’ve created this product after the custom fields (with default values) so I didn’t notice anything until yesterday that I needed to edit some text in one product. I edit the text, click publish, it says the product updated but it doesn’t.