Probably not a dud. Wrist HR is not a prime time product for athletes. It is OK with me, but I abandoned it years ago and use a Scosche or TICKR FIT arm strap. I have never tried wrist HR running or cycling on my 945-- who knows, it might be great for me now. (It is freakin' great in the pool, but that is because nothing else works for me there.)

Where wrist HR seems to lose it are:

1. Just doesn't work - often due to skin color or opacity
2. Cadence lock - needs to be worn tight to avoid this
3. Lag - I suspect error filtering causes wrist HR to lag or miss peaks entirely

I wouldn't knock it. It may not work for you. Plus, the 235 was an early (or first) gen HRM sensor for Garmin.They have made vast improvements since then.