Turning off sceeen but phone is not locking while usimg sms app

[ahmetborazanci]

Since I am upgraded to 5.1.1 ,sometimes,after i used stock sms app and press the lock button.Screen turns off  and everything ok.But if i quickly hit the button again i can see that phones is not locked.My friend told me its z3c's specialty.But it makes no sense.If i try this 10 times,aprox. 3 times screen is not locking.And i am trying to hit the lock button as soon as pressing the lock button first time.Curious thing is ,this never happened in whatsapp or any other sms app.The thing that bothers me,i send a text ,lock the phone.At that moment if i am not looking the phone, i am depending on if there is a message for me phone will ring.But it doesnt. Because the phone is not locked i can't hear any notification.Just the screen goes on.I tried to factory reset/hard reset but no chance.

[Thommo]

Try performing a system repair using PC Companion as this will often fix issues - This will factory reset your phone and erase all data so best to backup before you begin

Switch off your phone and unplug from Pc (Hold volume up and power for around 10 seconds)
Start PC Companion and select Support zone then Update my phone/tablet then in Blue Repair my phone/tablet and follow the on screen instructions - When prompted connect your phone still switched off holding volume down or back button - This should start the repair or reformat process

If you are using Windows 8/8.1 or a 64bit operating system then adjust the settings for PC Companion and run in compatibility mode and chose Windows 7 or XP

[ahmetborazanci]

I should have seen this coming I tried to repair/factory settings billion times old firmwares and new firmwares.So there is no solution.Thanks anyway