Xperia SP 12.1.A.1.201 unbelievably slow now... Help!!!

[SOS3v5]

Since updating software to version 12.1.A.1.201 on Friday 11th April 2014 my 4 month old Xperia SP is now practically unusable.
It is so ridiculously slow...
Cannot use contacts
Cannot answer calls... Screen stays blank, and caller quits before I can see who it is
Cannot enter messages .. Just freezes
Continuous messages... This app appears to not be responding, wait or close
Battery drain is terrible. Using power management stamina mode I could get 36-48hrs battery life. Now, I am having to charge every 6hrs.
This is a terrible, untested, software update.
So how to resolve???
I have done two factory resets... Which did not resolve anything.
The software is not settling down...

I need help, from an SONY employee, in plain English (not a lot a techie babble or loads of irrelevant suggestions that litter these forums.), so that I can rectify this problem and be able to use my 4month old phone again.

[Warbastard]

Thanks for the quick response frantizsekk.
I had a quick look at flashtool and it says warranty will be voided. It also talks about unlocked boot loader?
I'm not the most techy person and I'm not sure about it.
What exactly is flashtool and what does it do?

[blackbox]

That's Sony's flashtool. You want this one (no unlocking required, so warranty should be OK):

http://forum.xda-developers.com/showthread.php?t=2658952

[Henry24900]

I have the same issue after Jelly Bean Update Phone is working Very Slow, Extremely Slow, This phone is no even that old, is very good phone but this update just make this phone a unstable, and is not working at all, we deserved to get software fixed, at least a new update should be release to fix all the issue that we are getting

[Henry24900]

Same Issue Here, Exactly the Same Issues, we deserved Sony take hands on this and fix it, Several Users are reportly the same issue

[JossoSan]

Me too. It's the exact same issue.

[frantizsekk]

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@Warbastard wrote:
Thanks for the quick response frantizsekk.
I had a quick look at flashtool and it says warranty will be voided. It also talks about unlocked boot loader?
I'm not the most techy person and I'm not sure about it.
What exactly is flashtool and what does it do?

---

Flashtool puts firmware into your phone(ftf file) No unlocking bootloader is needed, Flashtool is only capable to do it.

Simply download firmware, put the file into  path.../flashtool/firmware, thn run the program, click on flash, choose flashmode, than the firmware file and than hit the button.

[wdv]

Repaire software with pc companion. Just wait a few days. Phone will become faster!

[SOS3v5]

Still waiting for a professional informed response from Sony... All the other third party best guess suggestions are totally ineffective and creating more problems. (It would appear that Sony tech employees do not visit this forum.)

[_alexdon_]

See here,maybe it helps if you disable chrome:

http://talk.sonymobile.com/t5/Xperia-SP/Solution-found/m-p/647611#U647611

[matt_pl]

After upgrade to 4.3 (266) my phone is extremely slow. Ive disabled some stock apps, but it gave no or little results. Chrome version is 28.
Update 201 brought a slight improvement in performace in the beginning, but after 2 weeks it's now even worse than 266.

It's a joke from Sony that I'm forced to learn to use developer tools such as Flashtool to bring the phone back to normal - that is downgrade the phone to 4.1.2.