Happens fairly consistently and has done across several software updates now.
If I navigate with Google maps and successfully reach my destination so that the maps app shows 'Done' but leave the phone on this screen long enough so that the phone locks it's self, trying to unlock the screen just gives a black screen that is largely unresponsive and displaying just a home button and a back bottom (both unresponsive) on a fully black screen.
The only screen element that now works is the notification panel - accessible by swiping down as usual.
From here the only way I can unlock my phone is to hope a text or email notification is active, whereby I can press on the notification and I am then prompted to enter my unlock code taking me to the email or text message app. From here I can then use my phone as normal again.
Anyone else have this issue or a cause/solution?