How do I fix an update issue that caused my Galaxy S6 Wifi Auto Reconnect to stop working?

[Android Central Question]

Last fall my US Cellular Galaxy S6 had either a software update or a security update on my Android 7.0 software which started causing wifi issues.

Before the update, my phone would automatically connect to previous remembered wifi connections, but after the update, it connected fine, but after about 10 seconds it would disconnect. At first, this only happened with my 2 wifi connections at home.

I would have to turn my wifi off and back on for it to connect again. Then it would disconnect after about 10 to 60 seconds again. Over and over my wifi only worked for less than a minute.

The only way I could get my wifi to stay connected was to turn on airplane mode. When airplane mode was turned on, my home wifi worked great!

Eventually this same problem started happening at work and at my parents. It would connect, then disconnect after a few seconds, but worked fine with airplane mode turned off.

I went into my settings and clicked on 'forget network' and got rid of all wifi connections that my phone had issues with. Then restarted my phone. I turned my wifi back on and it found my home network. I typed in the password and it connected... only to disconnect after a few seconds.

I tried my guest wifi and typed in the password and my connection was great as long as I had my airplane mode turned on. All was good for about a month when the airplane mode no longer fixed the issue.

Eventually when it disconnected, the wifi icon at the top of my screen would change to show full signal, but it would have an exclamation point with it. A message said something like 'connection failure' and I would have to disconnect and reconnect.

Now the only way for my wifi to stay connected is to turn off auto reconnect. I must manually go into settings and choose either my guest wifi or home wifi for my wifi to connect.

Once I connect, the connection stays on until I turn my phone off for a few minutes. When I turn it back on, I must manually choose the wifi connection again.

If I have 'auto reconnect' turned on, it will not connect to my wifi at all. If I turn off 'auto reconnect', my wifi works great after going in and choosing the connection manually.

I tried the same thing on my wifi at work and at my parents. The wifi worked great again as long as I manually connect and leave the 'auto reconnect' turned off.

All this time, my US Cellular mobile data has worked flawlessly. The problem is only with wifi connections. If I had unlimited data, I wouldn't care about the wifi issue, but I need wifi with as much as I use my phone!

How do I fix the wifi issues?

 

[Rukbat]

See if US Cellular has a brick and mortar store near you. If they do, see if they can flash only the update (so you don't have to back everything up). If not, try XDA Forums to see if anyone has posted an update file for your phone for US Cellular. Last resort - see if the company (tech support, probably level 2 supervisor) would be willing to do it without resetting the phone.

If none of those work, back everything up and reflash the firmware.

It's nearly impossible, but it does happen that an update goes bad and doesn't get caught and "not done". I had a Note 3 stuck between KitKat and Lollipop - weird situation, but since everything was backed up, I just reflashed and was done with the problem. (I always fully back up every phone. They're computers. How can you not periodically back up a computer?)