Sadly my 830 is heading off to MS for repair (UPS collected on Friday) as it kept randomly rebooting, sometimes with me using it, sometimes without. After I installed WhatsApp (probably unrelated) it went into an uncontrolled reboot sequence, where only a Hard Reset using the buttons would work. Very annoying!
Spoke to MS, they suggested using the Recovery Tool, nope, an hour later it started rebooting again.
Hopefully it's something they can either fix or give me a replacement.
On another note, I don't have the back cover falling off issue, however my Nokia logo is rubbing off.
I might wait for the new Win10 phones and swap out then. Bit disappointed with the build quality of the 830. Previously had the 820, and before that the 520, both had no issues.
G.