The blue warp, advancing reliably for a few weeks, no errors in sight, is now at the point where it must be declared finished.
I've cut the fabric off, serged the edges, washed & dried it, and removed all the thrums from the loom. Not surprisingly, this is what I found under the loom: blue dust bunnies!
I believe they're close relatives of the stuff I find in the lint trap of my drier.