UserAgent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0

Example URL:

Steps to reproduce the problem:
1. Login to PrestaShop backoffice
2. Go to catalog-products
3. Edit product

What is the expected behavior?

What went wrong?
Changed content is stored on the third or at fifth attempt.

Does it occur on multiple sites: Yes

Is it a problem with a plugin? N/A 

Did this work before? Yes < 50

Does this work in other browsers? Yes

Chrome version: 54.0.2840.71 m  Channel: n/a
OS Version: 10.0
Flash Version: 

This is a very big problem, because many people who have used e-Commerce, moving to other browsers to work stably.