Open the Menu and go to the License screen
At the bottom of the License screen selected the Uninstall. After confirmation, Boombox will be completely removed from the workstation.
WARNING: the audio library will also be uninstalled and will be unable to be recovered.
A manual uninstallation with a ZXP Installer should resolve any bugs you've encountered with the built-in Uninstaller. Grab one of the free third-party ZXP installers below to uninstall.
ZXP Installer: https://zxpinstaller.com
AEScripts ZXP Installer: https://aescripts.com/learn/zxp-installer/