Urgent Shopify Expert needed for urgent Fix

I need an experienced Shopify developer to urgently fix inconsistent Add to Cart, Buy Now, and Checkout behavior on a Shopify store using the Motion theme.

The issue presents as:
Add to Cart working inconsistently across products
Different behavior between desktop, mobile, and incognito mode
Cart drawer, Buy Now, and Shop Pay not behaving consistently
JavaScript errors affecting cart and checkout events
This is not a redesign or CRO job.
This is a functional stability and bug-fix task only.

The goal is:
One consistent cart → checkout flow
No broken ATC / Buy Now buttons
Reliable behavior across all environments
Theme: Motion (Archetype Themes)