Hola, esto fue lo que hice, pero el menú al que se entra con el *#0011# ya no es igual en MM y Nougat.
Solo pude cambiar el canal del router y poner la ip manual, de allí con la 6.0.1 phe se soluciono.
Possible fixes for Galaxy S6 WiFi problems:
Factory Reset
“Forgetting” your Wifi Network and Reconnecting
Settings ->Wi-Fi. Hit menu then Advanced. Make sure Keep Wi-Fi on is set to Always.
Settings, more networks, mobile network, uncheck Connection Optimizer
Under the Wi-Fi settings uncheck "Smart Network Switch"
Resetting the Modem/Router
Settings→wifi→WPS Button and same button on modem/router to 'lock on'
Switching from DHCP to Static Connection on Phone
Connect to your router's 2.4GHz band instead of 5GHz
Install a DNS changer app, select primary/secondary servers to Google or yandex.
Changing the Router Bandwidth Settings
Changing the Router’s Broadcast Channel
Adjusting the router security settings to WPA or WPA2
Enable WMM in your router settings
Disable IPV6 in your router settings
Calling your ISP and upgrading to a Higher Bandwidth/Speed
Wipe phone cache
1) Power off the Samsung Galaxy S6
2) Hold the power off, volume up and the home button all at the same time
3) After some seconds, the Galaxy S6 will vibrate once and the recovery mode is started
4) Search for the entry called “wipe cache partition” and start it
5) After a few minutes the process is complete and you can restart the Galaxy S6 with “reboot system now”
Disable phone's wifi power saving mode
1) Open your phone dialer
2) Enter *#0011#
3) Select more (top right)
4) Select WiFi
5) Turn off WiFi power save mode(enabled by default)
6) Exit and hopefully your WiFi connectivity issues will no longer be a problem
https://forum.xda-developers.com/gal...pping-t3079504