Got it! Because of some advice I got elsewhere that, "dogs don't wear out", I decided to have another look. What I found was that the dog retracted properly when I operated the machine manually to check the height and all that. But as soon as I switched to the motor and got it up to speed, the dog started "floating' and staying above the plate. It was pushing then pulling at the same time. So, I shot more PB Blaster on all the mechanisms that looked like they related to the dog and whatever was hanging it up loosened up and it works great now! Thanks to all for your input.