Shopify Cart Quantity Selector Fix

A recent theme tweak disabled the quantity picker for one particular SKU on my Shopify store. I now need the selector visible and fully functional again—but only for that single product, and only in the cart once it has been added. The quantity field on the product page itself should remain untouched.

I expect a lightweight code edit (likely in cart.liquid and related JavaScript) that cleanly re-enables the selector without affecting any other items or core theme updates. Once finished, customers must be able to modify the chosen product’s quantity directly in the cart, with normal price recalculations and no theme glitches.

Please let me know your approach and an estimated turnaround; I’m ready to provide theme access right away.