There is a way to fix this. The cause is related to an update of the Facebook App which is incompatible with the current phone system. I had the same problem with Facebook Messenger App. My solution was to replace both Apps with earlier versions. First, turn off Automatic updates so that they don't get updated again.
This how to do it -
Start by opening the Play Store app.
Next, tap the slide-out menu button in the upper left corner, as denoted by three horizontal lines, then tap Settings.
On the settings screen, tap Auto-update apps.
On the next screen, you’ll be able to choose whether you want to allow apps to automatically receive updates over Wi-Fi, whether you want to allow apps to update at any time, or whether you want to manually install all updates.
For the sake of this how-to, we want to turn off auto-updates altogether, so go ahead and tap 'Do not auto-update apps.'
(I am not an employee of Vodafone New Zealand and i am not associated to the social media team. I am a regular Vodafone New Zealand customer that volunteers my time here to help make Vodafone a better place for all)
My first smart ultra 6 froze and was replaced, my second is at the repair shop now having lost microphone, but I still like the phone and Vodafone stand behind the warranty, the only thing I'm worried about is that next time it might not be within the warranty period.