iPhone 5s WiFi turned off automatically and phone freeze

I have an iPhone 5s running iOS 8.3. I have found that iOS 8 is having some WiFi issues. But my problem is something else. Sometimes suddenly my WiFi connection gets disconnected. Sometimes it gets connected automatically. Sometimes if I manually toggle WiFi on/off then also it gets connect.

But sometimes when I try to toggle the WiFi from the settings app or from the control center entire phone gets crashed, stuck (freeze). So I have to press and hold Home and Sleep button to restart it. After the phone restarts the WiFi works perfectly until it automatically disconnects again and the WiFi toggling crash happens.

I have triedresetting the Network settings, Reset and setup as a new iPhone but nothing works.

Further Details

1. I don't know whether these are important to the WiFi issue. Only one side of my lightning port is working. (I saw a discussion that says it needs to replace the port, but I am in Sri Lanka and there are no official technical supporters here)

2. As I mentioned, I do force a restart by holding the Home and Sleep buttons when the phone gets stuck. It also restarts automatically If I keep the phone without doing anything. but when it restarts automatically again the phone gets stuck (freeze) in the lock screen, when this happens status bar contains everything expect carrier name. Even after this If I still don't do anything a blue screen appear and the phone restarts again. Then it works fine. (until it automatically disconnects WiFi and WiFi toggling crash happens.)