No, never get error .just http cod 302 ,and return home page

sorry . i can't understand. I need region everytime. There's no way to get region when region field is input?

yes ,i use $request->getDestRegionCode(),but if region field was input type field before select address in this time,this time $request->getDestRegionCode() return null.

dropdown can get right value , input type return null.

magento.com/default/rest/default/V1/carts/mine/estimate-ship‌​ping-methods-by-addr‌​ess-id select address ajax send request to this url ,param is entity_id in table customer_address_entity. use entity_id can find address and region has right value but region_id is 0. In this mode of operation getDestRegionCode() return null.