Failed updating and uninstalling app with ADB

I installed Better Battery Stats (BBS) v2 from XDA and quickly realized that the actual required version is 2.1. So I tried to uninstall BBS via ADB but that failed because BBS is a system app. Now when I try to install the new version, I got: bash-3.2$ adb install BetterBatteryStats_xdaedition_2.1.0.0_B4.apk 3925 KB/s (3671858 bytes in 0.913s) pkg: /data/local/tmp/BetterBatteryStats_xdaedition_2.1.0.0_B4.apk Failure [INSTALL_FAILED_ALREADY_EXISTS] And when I try to uninstall it, I got: bash-3.2$ adb uninstall com.asksven.betterbatterystats_xdaedition Failure [DELETE_FAILED_INTERNAL_ERROR] Can anyone point out how can I resolve this issue? I just want BBS 2.1 Beta. I am using a Nexus 4 running stock 5.1.1 (rooted).