Question: I'm using Apple's Core ML to visually recognize items in an image but it's returning incorrect answers sometimes identifying shoes as a knife etc. Is there a way to provide feedback about CoreML and hopefully guide it towards correctly identifying the items in an image?

Answer: 
You're probably giving the Core ML model inputs that it does not expect. I wrote a blog post about the most common mistakes: <http://machinethink.net/blog/help-core-ml-gives-wrong-output/>
I would open a feedback ticket at <https://developer.apple.com/bug-reporting/> 
Apple is really glad to get devs feedback. Try to detail yours as deeply as possible :)

EDIT : I would also suggest that you try another CoreML model ! I had a few tries with Inception V3 which worked like a charm with my apps. <https://developer.apple.com/machine-learning/>