I replaced the light seals with new foam adhesive weatherstripping and the GOO is GONE! I printed several negs in a couple of different formats and there were no spots. Previously there would have been a half dozen or so showing up on the first print. My guess is that the old foam was giving off small particles as it deteriorated with age. These particles would then float around inside the bellows and land on the under(emulsion)side of the neg after the neg holder was inserted inside the enlarger. I'm hoping this is the last of this particular problem.