Ah OK, you are using your own model, very cool. It is possible that the 16khz isn’t the only issue but it is definitely going to interact with any other issues on the older devices because that’s a lot more analysis to do.
Probably it’s best to start out by showing the logging from the iPhone 4 from an incident when it is showing this issue so I can get a look at which stage in the listening loop the behavior is happening in, and then we can look at possible causes and maybe find a way to fix or improve the behavior (I can’t guarantee there is a fix for this since it isn’t one of the models I ship, but I’m happy to work with you to try to improve things). It’s fine removing the vocabulary from the logs, but do let me know the reported size of the vocabulary so I can get a sense of what we’re trying to do here.