Sony XZ Premium won't turn off

[98058068]

I'm on my 3rd XZ Premium from the same supplier.  In every case, attempting to turn the phone off (as you would for air travel) causes the phone to hang - showing the powering off message (for up to 20 hours).  Nothing else happens and nothing else on the phone can be accessed.  A Sony rep showed me the reset sequence (the supplier didn't know about it) but that isn't working either.  Any assistance would be very much appreciated.

Some other quirks.  When sending a text message, using the backspace key sometimes causes the screen display to enlarge by at least 4x normal size, within an orange border.  The backspace key then produces a letter input.  This has happened with all the XZs I have had and can only be resolved by coming out of the text facility and re-entering (the message is generally as it was before the malfunction).  Again, the thoughts of those far wiser in these matters than me would be gratefully received. 

[najodleglejszy]

huh, that doesn't sound right. you should try performing a software repair using Xperia Companion on PC.
it's really weird that it's happening on more than one phone, perhaps the supplier has got some borked batch.

also I really, really hope it's not the case, but if it's a third party supplier, perhaps it's a knock-off phone? did you try logging in https://mysupport.sonymobile.com and adding your device's IMEI number?

[Karim]

Can you post a video of what's going on ? I suspect a fake unit ? 

[98058068]

Thanks for the advice. Latest replacement is a chrome finish XZ rather than the previous black versions and so far so good. So perhaps a bad batch. 

All XZs supplied by same, well known, national High Street retailer. 

[98058068]

Thank you for your help.  My earlier response applies. 

Regards