Address not saved

Hi i’m trying to understand why your plugin is not saving my shipping address from checkout on my website.
From what I understand, natively woocommerce saves from the checkout the last used adress in the user meta . You prevent this and add the last adress to thwma_custom_address meta, is this correct ?

On my website if your plugin is not active the address is updated in my account page.
But with your plugin active the address is not updated in user meta and the address not saved..
Could you explain me how the function set_first_address_from_checkout works ?
Do you have an idea of what is happening ?
Thanks