I will be sure to go through the stopstep more attentatively. That may well be the problem. I give it a solid 85% probability, but will still have to test tomorrow.
But I have to disagree with the newton ring part of your answer. . .newton rings appear worse when the pressure between two smooth surfaces is increased . .glass to glass, filter to filter, negative to glass (usually the non-emulsion side is affected worse) and so on. Often the easiest way for me to solve newton rings on the rolls of film is to "soften" the vacuum pressure on the negative. And I was to understand that with you folks' enlargers there can be a problem in the glass to glass negative sandwich with newton rings. I know that my contact printers also newton rings the most under the most vacuum pressure.
Anway, I suppose there is a way to see if his hands did this, but it will be a couple of days till I can someone up here to push on one side of the copy board with paper in place while I evaluate the other side of the glass.
Thanks again so much. Ed, you ROCK!