Here we go again.
Last month Google released its first Maintenance Release for Android 5.1 Lollipop, and while it did bring in a few features, improvements and bug fixes here and there, users found another memory leak issue that caused the Settings app to consume up to 100MB. The problem was then fixed and pushed to AOSP.
It only makes sense that the fix would come in an incremental update, which now shows up on Android’s SDK Manager application as Android 5.1.1. It’s worth mentioning that there are several Nexus devices that haven’t received the 5.1 OTA or factory image, such as the Nexus 4 and 9 so hopefully they will end up receiving Android 5.1.1 shortly after its release.