I have found the fix. Not the themes problem but Prestashop. yes it was mod_security rule
which we disabled for our domain.

Important notice :

Our awesome Jérôme just found the reason why this “Save” button was not working or taking forever to load. He is adding the fix in version which will be released this week.

Please note that after you update to, saving your product might take 12 seconds for some of you who have “Evasive mode” activated on your server. The reason is: when you save your product, you send 12 requests (one for each tab of your product page) to your server and to prevent mod_evasiv DOSPageInterval to block your requests we must slip 1s between each call. If you want, you can contact your server administrator in order to change DOSPageInterval.