Ok I've had this problem for a couple of months nah and I have just figured out wt happen believe me I've tried every single thing Apple said to try every single thing all these forums said to do and guess what I have figured out. It's not the board or no let me not say that here is what is causing it to go in search or no signal mode. We like to place our phones in our pockets, back pocket front pocket and this causes the phone to warp, thus causing some internal problem for the first time in months I use my phone but here's the trick the signal would come and go so wt I did when it goes is I hold the phone like I'm holding a glass, hold it tightly the push on the top left firmly while holding the bottom firmly like a glass and Boom it works. It lost signal again three times today but when I repeat this step it comes right back in so what have we learn today. Don't sit or place your phone In your pockets and I will continue to do this till I can afford a new 6plus. I hope this works for some of y'all but I'm so glad it's working for me. I guess the drop test is similar cuz it twists the phone once it it the ground but hat didn't work for me. Good look guys