Woocommerce Shipping Fees not Calculated accurately on selecting/changing Zones

I’ve already set zone shipping flat rate fees for Zones (shipping only for country: Lebanon and Zip Code is not applicable), but client are facing 2 issues
– When selecting the “Town/City” from the drop down its showing that there is no shipping method for this zone, so they have to fill the region name in “state/country”, which is optional field, to get the region name matched.
– If any client filled the region by a wrong one and needs to change it, after changing it the old one will remain matched and the fees will remain for the old, and to bypass this issue the client should re-enter the checkout page again.
Note that shipping calculator in the Cart is working properly, by selecting country and “Town/City” from drop down menu.
I tried woocommerce shipping calculator setting in booster settings and unchecked the “state/country” but it didn’t help, also I tried hiding the “state/country” field but also at checkout kept returning the same: no shipping method, or keep calculating on last shipping “state/country” if it was filled before.
Is there any trick to bypass this or it is a bug that should be fixed?
Thank you.