add-to-cart Shopping Cart Bugging Out

Site URL: https://www.lbstructural.com/

Is anyone experiencing Cart/Checkout issues? I am adding products to cart and when the cart is clicked on, I get the empty cart notification. A refresh brings the products added back temporarily.  Is anyone else experiencing this? 

I have a similar issue too, sometimes cart says it has 1 product in it while it's completely empty. Sometimes it shows a +1 in number. I tried disabling every custom code for the cart but I noticed it is a Squarespace issue