Button error decreases / increases objects in the cart

[Totonno]

Goodmorning everyone...

I can not solve a problem that appears in the shopping cart. When I go to the checkout page and see the content of the cart is all working but if I want to increase or decrease an object by clicking on the up / down arrows the figure changes exactly but the arrow box disappears and I exit the text field with inside the number of items I'm buying.

To return the arrows panel I need to refresh the page.

Precisely that I have prestashop version 1.7.2.0 and that I use a theme purchased. With the default theme "classic" this error does not occur.

I do not know where the error may be in the css file or else. I just hope someone can help me.

Greetings