> I adapted the traditional whiteboarding exercise
Lots of engineer types freeze when they have to make a presentation. I remember a meeting early in my career with literally three people in a conference room and I almost had a panic attack. No white board. People I already knew. All I had to to do is explain my ideas to three people. I did improve. I've given many public talks sometimes to hundreds of people and today I like public speaking. But I'll never forget where I started and that the person I'm interviewing might be very nervous. Putting them up on a whiteboard and into presentation mode only amplifies that nervousness. Just talk to people. Get them into that flow that comes from talking about something familiar that they are excited about. For most people a whiteboard test is not exciting. But if you give me a paid take home coding exercise, that's exciting. I like code, and I like to get paid for it. So if you really think you need a test, consider a very high signal test that is the exact work they will be doing.
> I make sure to ask for feedback on the exercise and I've gotten all positive feedback from candidates.
In an unequal relationship like that you are going to get a lot of false positives. If I really needed a job my response would be "loved the exercise, looking forward to talking to you more and discussing next steps if I'm the right candidate".