Why does the default variant get added to cart regardless of customer selection?

Hello,
no matter what variant the customer chooses, the default (first) one gets added to cart and we have to ask each customer by phone on what size they wanted.
I did not alter the code of the product template in the sections related to variants or ATC but I did on elements below it (ie. product suggestions with metafields).
We use Cozy theme and the one add-on that might interfere would be “Product Filter & Search”.
Browser console shows no related errors.
Attached is the full product-template.liquid file.

• URL to check is: https://www.locapica.com/collections/rochii-de-seara/products/rochie-de-seara-electra-midi-petrecuta-cu-paiete-verzi

• Default variant is smallest size (ie. 36)

• I have hidden the second variation element (color) in CSS as we only have one per product and we just use it for the products filter

Relevant snippets for assist:
• Button type variants list:

{%- when 'variant_picker' -%}
                      {%- unless product.has_only_default_variant -%}
                      {%- if block.settings.picker_type == 'button' -%}
                      

• Add to cart:


                          

                            
  
  {% if section.settings.enable_payment_button %}
                            {{ form | payment_button }}
                            {%- endif -%}

{{ 'products.product.notify_me' | t }}
   
                          

Hello @Attrexx ,

  1. Why variant code is outside the scope of form tag.
  2. Compare your variant change functionality with the theme preview. I mean check a product in the theme demo and notice if there is a change in URL when variant changes. I think variant ID changes in the URL when variant changes.

Thanks

Theme preview option changing does not alter the URL.
Theme preview shows same code structure as our site (like I said, we did not alter it).
https://theme-cozy.myshopify.com/collections/fashion/products/exercita-tionem-ulam-1