I have had my trusty old phantom 4 Four years with out a problem, have always loaded firmware updates with out a hiccup, I have only had battery problem when over charging best if you store by the book as low as a discharge you can get them without being Flat no power about 1 light.
Never give up on the simple things: have you got a new set of props if so have a go at that. To me, it seems like an aircraft balance thing, even swap props front to rear and note any different result
First and utmost you should check the pitch of the new prop best way when a prop is damaged is to replace all 4 Are you sure the motor shaft is not damaged (bent)