There was a threading error....... I discovered it as I was throwing the initial plain weave shots to ready the warp ends for weaving. There were three warp ends next to each other and they were working as one. That means that when one of them was up so were the other two. And when one was down, so were the other two. This is not plain weave!
These three warp ends were the first three on the left side of center. I remember when I was threading. I had started at the right side of the loom. When I got to the center I hadn't quite gotten the heddles counted out right. So I had to do some moving around of heddles between the right and left sides of the shafts. And somehow in all this finagling, those first three ends at left of center ended up on shafts 2,4,2. Well, in crackle it doesn't matter what the threading is supposed to be, this was definitely wrong. In crackle, you cannot have threads next to each other on either even shafts or odd shafts or you are not going to get tabby.
When I investigated, it turned out these threads were supposed to be on shafts 1,2,1. If I had mistakenly threaded 2,3,2, that would have been logical. I would have just been off by one shaft. And I'm not sure I would have even caught the error since the tabby sheds would have been just fine. So my head or my eyes must surely have been muddled. Probably I should just be grateful that if there was going to be a threading error, it would be one readily apparent.
Anyway, out came two repair heddles from my supply. I put them on shaft 1, pulled out the three mis-threaded yarns from the heddles and put them in the correct heddles. I then sleyed them through the reed. Since these ends were now short, I tied additional thread on each of the three threads. This made them long enough for me to secure them to the web with a pin. When The knots were right at the fell so they never interfered with my continuing to weave.