Just in case that it could help someone, the problem was with memory release of strings passed from an audio plugin to the CoreAudio server. They are released by the API in OS versions prior BigSur, they had to be released manually in 11.1 and 11.2 and now they are again released by the system in 11.3. Double deallocation led to the core dumps...
One extra feature (not sure if it was added in 11.3, but it causes plug-in stability problems): when you write something into the plugin (i.e you have a property with "IsDevice,Control,StreamPropertySettable"=true), the client app must have Apple Events and (still not sure why) Calendar permissions allowed in the app capabilities.
Topic:
Media Technologies
SubTopic:
Audio
Tags: