@Myphonefail. I have also change my battery to a new one a month before the update. My screen is working normally but my iphone is anyway very laggy and crappy. I would expect that it is maybe because of the screen that my phone is not working properly ? Can you please confirm that your iphone still work fine after changing both screen and Battery?

Never mind, It didn't help...

Hello All, I have tried many thing to solve the issue unsuccessfully and what seems to work for now is the following (it has been 2hrs without any lags): I set the iphone into DFU mode and restore it as new iphone from itune on my mac. I will keep you updated if this end up to be failing again. Cheers,

Hello again guys, The reset to factory without backup is not working finally. I have been on the call with senior guys from apple and nobody can help nor give me a replacement. Apparently we are not enough ppl having the issue so I filled a official complain to apple to see what they can do. My best guess now is to unofficially downgrade the phone and see if it works

After talking with Senior Consultant at apple, it seems that the software is glitch and the only fix is to reset the phone to factory setting and not using any backup. It seems to work for me but this is freaking annoying.

Exactly the same thing, Since a little while my battery get drained like crazy and I even changed my battery to a new one and it doesn't help. Now with 14.2 my phone show me whatever battery percentage, sometime reset when plugging to the charger and the volume button is just crap and lagging as hell.