OK I’ve find out what’s happening.
The event had long trailing silence and as long as event was active the new upcoming events were also routed to the controller speaker.
Now I realize that every time I want to play some event on controller speaker I need to attach the ChannelGroup to the appropriate port.
I’m not gonna lie the design of this isn’t very intuitive and I’m not sure if it’s documented anywhere (at least I didn’t find it).
I’d expect that if I have group under the port in FMOD Studio that it will play on the desired speaker all the time. I understand the requirement of pointing to which controller sound should play but maybe defaulting the sceUserServiceGetInitialUser for controller speaker and vibration would reduce confusion when using controller features with FMOD.