I have never had any WiFi issues with my note 3. I consistently get 55mbps+. I did have some WiFi calling issues when I was on 4.3 after messing with some xposed modules and using a custom ROM, which was known for WiFi issues. But I have my router set to 5ghz. I use the upper extension channel and 40mhz channel Width. I use a custom router software called ddwrt.

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