I'm experienced with weight-based calculations in the Shopify Checkout API.
Specifically, when I pass a weight value of 5000 grams in a custom line item using the Checkout API, the weight shows as 0 grams in the checkout.
I've double-checked that I'm using the correct field name (grams) and that the value I'm passing is a valid integer representing the weight in grams.
I've also tried passing different weight values for the customs line item, but the weight always shows as 0 grams in the checkout. I suspect that there may be a limitation or error with the weight-based calculations in the Checkout API.
I've also attached a screenshot that shows the weight-based issue in more detail (https://d.pr/i/2RM35V ). As you can see, the weight value is being passed correctly in the API request, but it's not being reflected correctly in the response object.