Shipping address undeliverable, MissFulfillment promise but seller is responsbile

Hi everyone and Seller support,

I need assistance in this matter because I got more than 60 % to 70 % refunds due to the Shipping address being undeliverable and Miss Fulfillment promise.

The shocking thing about the Shipping address being undeliverable is that the buyers are repeated buyer when i asked one of the buyers you have ordered many times with us but this time your address is undeliverable what is the reason.

He told me that the order gets canceled automatically there is no such issue of address he is living at the same address where the previous order delivered before.

Due to amazon representative mistake i am getting loss and i am paying for the refunds.

I just want to know how can i get this fixed or get refund of fba fees because just last month i got almost 50 returns.