iPhone 6 No Wi-Fi Signal? -- Nothing seems to work

Sometimes it can detect networks if you are extremely close to the router. This issue definitely isn't software because I have reset all network settings and restored via iTunes.

I replaced both the antenna AND the flex cable, and it seemed to work fine afterward, so I put it back into my case and the problem instantly comes back. Since the case requires a lot of force taking it in & out, my theory is that when this happens it puts strain on the rear housing and damages signal.

So I decided to buy another flex cable and replaced that, but to no avail.

Is there anything I can do besides buying a new housing and crossing my fingers that it'll work?

(BTW: the phone is past its warranty & can only reliably detect 5Ghz networks, though not very good)

Thanks for your help/guidance, it's much appreciated

- John Baker