I have a Sony DCR-TRV120. I hit it 10 or 12 times (not too hard) methodically hitting different places. This is with a tape playing and the lcd out. With the lens facing away from me, the jerking stopped when I hit the bottom-left in front of the lcd. I'm curious if anyone else noticed where hitting it worked, could be useful diagnostically.
There's a wonderful short story about exactly this phenomina by Theodore Sturgeon from 1970, "Uncle Fremmis." An insightful and very funny story about a man who somehow knew just where to hit something to make it work. Or someone. If you Google Uncle Fremmis you'll see it in a couple of collections of Sturgeon's stories, especially "Sturgeon is Alive and Well," a great collection.