Nested form POST request that returns errors, still triggers GET

[ivosabev]

I have a form dialog that opens on top of another route like this:
/products - Route with products lists
/products/edit/10 - When you click edit on a product the form appears as an overlay dialog (the products list stays visible beneath)

On a successful form submission the form redirects to /products and a GET is sent to refetch the whole page.

On a failed form submission I get a funny request sequence

POST 10?_data=routes%2Fproducts%2F%24action.%24productId
GET 10?_data=routes%2Fproducts%2F%24action.%24productId
GET 10?_data=routes%2Fproducts

I tried returning 400 response from the action, but the GETs are called again.

unstable_shouldReload is also not helpful as it is not aware that there was a 400 error.

I would like to get rid of the two GET requests on error and only to have the POST request which doesn't refresh the page but returns the error data from the action handler that I can visualize.

The form is submitted with a submit button, not programatically.

What I am missing? Thanks!