Android 5.0 bug makes it a bit harder to close all open apps

The random app that appears, thanks to the bug, is one that you had open before you started to close the open apps. You need to have quite a few apps open before the bug does its "thing." And it is not related to any particular device, either. The bug has appeared on the Nexus 5, Motorola Moto X (2014) and the Nexus 7 (2013), all running Android 5.0.
Previous issues involving Android 5.0 included a problem with Wi-Fi connectivity that led to the battery getting drained. That bug was exterminated. Another problem with the latest Android build made it difficult for some Android handsets powered by Lollipop, to connect to a Wi-Fi signal.
source: YouTube, AndroidPolice via AndroidAuthority