Newbie auv3 installation question

[t0m]

Installing new Audio Units requires restart in High Sierra

Since macOS High Sierra, installing Audio Unit plugins seems to always requires a restart (or at least a re-login) before hosts see them. Even though we noticed it for all plugins we checked, some folks report that “some AUs require restart, some don’t”. Does anyone know more about this? Is there any special juice required for new AUs to be listed? If so perhaps this juice could be incorporated into JUCE? Is there something new that installers need to do?