looks perfect! SOunds like you have it almost "Dialed In" for optimum burning.
Yes, sometimes the plate moves up a bit, the plate or the pusher rod/bearing may not be perfectly level/even....as long as it's going back and forth, should work fine!
Once in while, You may hear a crunching or scraping sound when you get fines or small pieces caught under the grate, I have just dropped the motor down and move the plate back and forth by hand while pushing down and usually cleans it out. Be careful, you can push the fire off the grate if you push it too much. I have done it while it's burning, but not recommended.
Another Trick, sometimes you will get fines out from under the grate onto the motors, I had to put a cover over the combustion blower, since the fines for falling directly on the motor and can cause it fail if it gets into the bearings/shaft.