Can't checkout or add to cart - losing sales

[User01]

For some reason when you add to cart or if you click the checkout button in cart, it takes you to /search?q=&options%5Bprefix%5D=last&form_type=product&utf8=%E2%9C%93&id=37839505653948&quantity=1&add=/

I've spent a long time trying to figure this out and all I have found so far is that most of the forms on my site are missing the <form> tags. So if I look on an older backup of the site it works because the buttons are wrapped with <form etc...>. I've replaced the entire product-template.liquid file with the liquid from the working theme, however this still hasn't fixed it.

I did the same with theme.js, and theme.liquid.

Does anyone know why on earth there would be logic to look for "form" tags and remove them??? it looks like it's being done prior to page loading also.

[User01]

i've put dummy <form></form> tags at the top of the cart and product page templates and this has fixed the issue... but I still need to get to the bottom of what is trying to find the form tags and delete them. Such a strange issue.

[pioneer100]

@User01 , can you please share your store url so that we can inspect and find solution. 
Thank You

[User01]

Hi @pioneer100 I have emailed you the store URL