Wi-Fi not working on iOS 8.4

iOS 8.4 with broken wifi also drains battery. In 3 hours battery capacity dropped from 100% to 73% (loss of 27%).

I recommend users who experience wifi issue to completely disable wifi until Apple fixes the problem. It looks like device is occasionally scanning wifi networks while in sleep mode.

After you disable wifi, avoid enabling it again or even navigating to the wifi settings. The device may freeze. In that case you need to press and hold power button and home button at the same time. When the devices shuts down, power up again and don't try to change wifi setting, leave it off.

I think the device must be doing something on the background that causes high CPU usage, device slows down and after a few ore seconds it freezes completely. Clearly some multi-threaded deadlock in wifi or networking routines.

Another issue screen started flickering. iOS 8.4 is very unstable release.

Attempted to fix by following steps:

1. Disable Bluetooth - no luck

2. Disable Location services (I was thinking if assisted GPS somehow doesn't interfere with networking) - did not help

3. Remove SIM card and left only wi-fi - still nothing

4. Upgraded firmware on wi-fi router to the latest. Why would I need this? This requires some more explanation. Apple released iOS 8.4 with a fix for iPhone 4S where it should better match security settings of router to prevent iPhone to connect to a router which broadcasts fake SSID. Upgrading firmware on the router did not help.

No luck at all.

I'm thinking of trying another type of connection - perhaps WEP instead of WPA/WPA2

Another test could be changing channel number on the router - I'm thinking if some iPhones don't have an interference problem on certain frequencies. The wifi problem was reported on iPhone 4S, iPhone 5 and iPhone 6, so it is unlikely that wi-fi chipsets and circuit around it could have this kind of problem on so many devices.

Please share what you have tried.

Thanks.

P.S. I think Apple should be paying us for that or at least send us some devices for FREE. When a user of my app found a problem, I resolved it and despite that I offered this user a full refund + 3 extra licenses for friends/family, just for his effort and letting me know about this particular problem and his suggestions, which lead to new version of the app and new features.

More updates:

As I suggested I changed wi-fi channel on the router from Auto (which is 1 - 11) to 9 and managed to get wifi connection for about 2 - 3 seconds. I also tried other channels, but no luck. Channel 5 seems to be working a little better, but network dropped after a minute or so. If I remember there were some problems with wireless stability and Apple implemented some software fix. Perhaps someone removed that fix/hack, because that developer thought it is no longer necessary. Perhaps that fix could handle intermittent disconnections or variable bandwidth setting, who knows. But this could be our problem.

Right now iPhone has great difficulty to even scan for available networks.

It would be nice if Apple could publish the code and let us do code review or perhaps if we could implement the fix ourselves.

Screen on iPhone 4S started flickering again. Battery is at 85%. While recharging the device was flickering less at 87%, it was even less obvious at 89% and screen seems stable at 92%. At 93% of battery capacity, flickering is a little worse, but can be noticed only by peripheral vision. The device behaves as if oscillator was becoming unstable. It is around 25 degrees Celsius. This device is 3 years old and I'm thinking if deteriorating components aren't culprit of not just screen flickering, but also wi-fi.

However yesterday I put iPhone into refrigerator for a few minutes to cool it down to about 15 degrees and tested wi-fi at full battery capacity. Wi-fi still didn't work. It has to be software problem, because it worked on iOS 8.2 (on my device, although there were reports of wi-fi problems since iOS 8.0).

I attempted to completely disable router security, iPhone connects to the network and disconnects after a few seconds. So I guess the problem is not caused by Wi-Fi update in iOS 8.4, which improves matching of security parameters when iPhone 4S connects to wifi.