Strange bug with Presta 1.7.2 on product pages, please help

[JoeSchiaffi]

Hi guys, 

 

I've some serious problem here, a strange bug and cannot figure it out what it is: i've tried to disable all modules I've installed, but the problem remains:

 

Prestashop 1.7.2 (upgraded from 1.7.1.1, after upgrade I had not this problem, I've only discovered it today) default theme, If you open one of my product pages (all products are quantity 1, so If you put 2 ore more into the quantity box, Prestashop by default tells you that "There are not enough products in stock" and the add to cart button gets disabled by default (because I've choose not to let customers to order out of stock products) but The message "There are not enough products in stock" doesn't show up, it only disable the Add to Cart button, but what more: on my product pages, under the image thumbs, I have a Module that put youtube videos for every product: every time I change the product quantity the video keeps duplicating itself, I've tried to disable the youtube module, the preorder module, and all the other modules that I've installed but nothing, the problem still remains. I've tried to enable Debug mode and with that (I've disabled all cache and forced compilation) I got monster quantity of errors (see the attached TXT file).

 

Now i've disabled debug mode, you can test the bug in one of my product pages:

http://www.jollyrogerbay.it/shop/playstation-4/165-234-project-cars.html#/52-condizioni-nuovo

 

Please, I'm asking for help since I'm about to open the shop and all of a sudden I've got this problem.

Thanks

Edited August 12, 2017 by JoeSchiaffi (see edit history)