iPhone 6 - Wifi 2.4Ghz Very Weak, 5Ghz Works Good BT too

1. 5 Ghz works perfect
2. Bluetooth works perfect
3. GPS works perfect
4. 'WiFi signal 2.4 Ghz is very weak'

I read quite all questions posted here, the more I could not solve my problem.

I'm sure it is a hardware failure that has already performed all software testing

I tried a few things I've seen posted here ...

Images are illustrative and not real ...

I tried to clear the Wi-Fi contacts that are located in the upper left corner of the board logic. Unsuccessfully.

I removed all the logic board and tried to clean the contacts again, this time cleared the front and back ... also without success.

Multiple users suggest scratch the Wi-Fi contacts for better conduct of the board, also performed unsuccessfully.

And finally I checked if the plugs from the back of the logic board are four slots if they were correct, without success ....

Already exhausted attempts, does anyone have any idea?

Sorry my bad English ...