my lumia does this sometime if plugged in to charger,but im still using 7.5,think its a bug with the charger .just unplug it and its gone.....
All I can add is that I loved my Lumia 900 before but it's an absolute gem now with absolutely nothing to complain about. No problem scrolling. No over loud sounds that cannot be adjusted. Even the random reset has vanished and that I regarded as a good idea, apparently related to the velocity sensor thinking the phone has been set down with a call connected. No point running up a bill from user neglect. Just my take. Honestly, add a few Nokia extensions and I have to force myself to stop fiddling.
If you think it was a bg mistake then perhaps your should also think about checking out the sound level setting that's right there, then do the same on send for which the scale is altered from 0 to 30 to 0 to 10 and set the latter at 5.
Smooth scrolling? Oh YES it is, and more. Love my Lumia 900.