Chosen Solution
2,4 ghz wifi signal is very weak on a iPhone 6. It only work when the phone is beside the router. Just one step from the router and the signal is still there but weak and the internet is stop working. But the 5ghz wifi works well with normal range. I have seen this problem of a few iPhone 6. And i am sure it is hardware related, i have tried network reset and also a full restore with no succes. Is there a solution to this?
Check the screws and clips on the top bezel, and the flat RF bridge cable on the upper part of the phone.