I've had my ZTE Axon 7 Mini for 2 months now moving from a Nexus 5 (I know long time coming) but I have been struggling with some performance bugs when unlocking the phone. I tried speeding up animations to get that little bit of performance boost (or an emulated one) and it didn't work. The solution that I ended up finding out is disabling the "Always show nav bar" switch under the Navigation Bar settings did I find performance reliability increase. Found this out the other day and just thought I would share to see if anyone had the same issue.