mind-numbing detective work in progress
After disabling the erroreous box of spam product and still getting that error, I went back into CMP, searched for all category "Commodity" assets, added Location to "Local", selected all and disabled all. Then I added another parameter to the search, BuiltIn, which showed me only those that came with the game. I selected all, and re-enabled them.
Back into Surveyor, check out one of the Multiple Industry tracks on a cremery I added to IndustiRail 4a, and it was fine (although I was surprised to see the bottled milk commodity, not a built-in one, was still listed on queue 1!).
Back out of Surveyor and back into CMP, remove the BuiltIn filter, sorted by kuid #, and I found the rest of LLJ's products since he did most of the built-in ones, and enabled all of his. Back to Surveyor, and the MI track is still okay.
I went back and forth, enabling commodities slowly by author and all is still well. Unfortunately, my investigation had to be curtailed since 5 am comes too stinkin' early.
But it's clear that the culprit is an asset that was added. I will continue with my testing this evening, but with more than 500 commodities, it's slow going. But I will let you know when I apprehend the guilty party.