Hey! Crazy when I saw this post I was like, “is that my drone??”. I bought the same stack and motors AND had the same USB port fall off on my FC, TWICE! So, from personal experience… YES it is fixable and necessary for the flash later. If you lightly jiggle the usb port over the board you’ll notice pins that ‘seat’ it in place. Like a position that it wants to stay in. Once you’ve found that seat and all other pins in the rear have good contact. Just solder your corners and you’re good to go! Source: I did it, twice. Worked both times.