Something callback related would be my first guess - for example:
- Getting stuck in a user callback that is triggered when the system tries to release
- A user callback (typically with behavior that occurs when the system is releasing) not meeting the requirements set out in the Callbacks section of the FMOD for Unity user guide
If you’re using callbacks, especially those that would fire when the system is releasing, I would recommend making sure that the code there is safe and meets the requirements mentioned above.
Attempting to do something FMOD related (e.g. something like creating another system) from a different thread when the existing system is releasing may also cause issues. However, this is less likely unless you’ve modified the FMOD for Unity plugin heavily, or have a lot of your own custom editor code for interacting with FMOD.