[LG G5 Questions & Answers] Chameleon560:
Well, the investigation went on and, spoiler alert: There is no solution that easy as bending the pins or the right pins :(

To the questions:

The silver mesh is not really a design failure. Seen this in other phones many times and usually this is used for ground points. I do have plenty of exactly that kind of mesh. You can resolve the glue in isopropyl (99,9%) and look behind it. Nothing special, it's like the other contacts. I also tried to stack a bunch of that mesh to gain high. I even replaced the springs with other, bigger ones, but no, not a single improvement! As far as I can tell already: If once gone wrong, there is no permanent solution.

Soldering wires: Yes, I found the post with the wire guy, too. Since I do have proper soldering equipment, to solder even BGA parts, it was no problem to remove the antenna plugs and run a wire through (yes, the wire on the picture is insulated). Well, it does work, but just as long, as the case is opened. When you close the case and assemble it back together, signal is gone! Tried different ways, around the camera, around the lower part of the mainboard, no difference in performance, after the back cover is closed, all signal is gone. I also soldered the wires to the antenna pins with the same result.

I would never put solder on the golden shiny parts of the pins, because then you will definetely loose contact, because the solder oxidates. I did replace the pins with bigger ones and elevate them, but no difference. Another interesting fact: you cant solder the housing to solder the antenna to the housing!

To confirm my contacts, just open the phone, put the battery in and a rubber strap around it to hold it in place. then take a wire and short the blue marked pins to simulate the power button (hold it a sec). The phone will boot up and work normally, exept no antenna and fingerprint sensor is connected, so remove the security settings first. Then you can start your favorite GPS software, look for a fix and if there isn't any, put the finger on the upper pin and check again (give it some seconds to find a fix). You will see a major difference.

About the pictures:

GREEN: This trace I connected to the wires after removing the antenna plugs from the mainboard.

BLUE: Power button pins.

RED: GPS antenna trace I could find so far. Yes, in my other picture the trace is not 100% correct. I am sure that at least this pin is going to the GPS. The other trace to the back of the mainboard and the antenna wire might belong to something else. Since from the warranty GPS repair of my first G5 I got the WLAN / BT chip replaced and I tracked the path down to this chip, I am pretty confident, that GPS is also build in that chip. You can google its part number to find out more.

After all the testing I got a short in the antenna line to ground. My search ended on the upper chip of the WLAN/BT area beeing broken! You can search shortet broken parts by applying isopropyl (99,9%) and a weak current through the short and watch out where the isopropyl starts to get hot and vaporize. In my case it was pretty obvious at that part, which is shortet now.

Conclusion: The broken chip got shorted while testing, so I guess either the wire I soldered touched something, which is unlikely or the water damage of the phone gave it the rest OR the part is the problem in the bad reception, too.

Anyway you can't solve it by simply bending the pins. I did put in pretty big ones and elevated the whole thing to obviously get contact and had no succes. the pins even bent inwards after closing, so there was contact. I tried it many times with different ones to make sure they touch in the right position and finally I scraped the coating on the back cover to gain better contact and again, nothing!

I am out of ideas and now that my GPS antenna path is shorted to ground I can't test further.

If a had another phone I would do none of that and replace the back cover first.