I've been having the same problem..
I'm on Lollipop..
Everytime turned on the wifi/bluetooth.. it turned light green (not green as normal) and won't properly turn on
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Things I've tried...
Reboot
Battery pull (30 secs ~ 6 hours)
Edit some config file (rooted phone)
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1. Root your phone
2. Download Root Explorer.apk, put it on your phone via USB, install it
3. navigate to either /data/misc/wifi or /system/etc/wifi
4. rename or delete wpa_supplicant.conf
5. reboot
Boot to recovery - Wipe userdata/cache
Boot to recovery - Factory reset
Reinstall OS Update view Samsung Smart Swithc
All doesn't solve the problem...
Tried asking 2 3 shop.. they said probably IC damaged or something
One last thing I tried is ReDownload 5.0.1 ROM and installing via Odin
That *did* helps the phone somehow (the wifi / bluetooth is working at the moment).. but still failed 20% of the time (no connection even when connected to wifi... but no light green wifi problem)
Do at your own risk

I'm downloading this particular firmware now, will try to flash it later on.
Can you share what is the 5.0.1 ROM version u running on? Is it as the above? I saw from sammobile there is another older version with PDA I9500XXUHOH7.