Any time you are learning a new skill or working on a new weave structure or making something completely different than what you've done in the past you can expect mistakes. In weaving, at least for me, they all happen or reveal themselves in the first 3 or 4 inches of warp. Well, unless they pop up even earlier.
Part of warping the loom is threading the heddles. Heddles are long thin metal pieces that hang from the harnesses. Each one has a center eye through which you pass a warp thread. They hang from the top rail of the harness and also are attached to the bottom rail of the harness. It sounds straight forward but they are "slippery little devils" as Julia Roberts said in Pretty Woman. OK. She was talking about snails but I'm sure she would agree with me that heddles are just as slippery.
It's easy for heddles to get crossed. They nest with their buddies on or off the harness and don't lay exactly flat when you are trying to arrange them. Once you get them hanging on the top rail it's easy to assume the bottom ends are where they should be so you can slide them onto the bottom rail. Nope. Not necessarily. Each harness may hold over 100 heddles and on an eight harness loom that really adds up. The harness has to be half torn apart to add or remove heddles. It's a royal pain in the bum. The only way to verify that you have no crossed heddles on your loom is to use every one of them. It's pretty much impossible to tell they are crossed until you try to thread them. There was a time when I would very carefully take all the remaining heddles off a harness to get at the crossed ones so I could get them uncrossed.
No more. Now I pull out my trusty wire clippers and cut off the offending heddle. Snip! Snip! And we are fully functional again.
After the heddles are threaded, all the warp ends must go through the reed. It's call slaying the reed. I'm usually pretty good at it and if I do make mistakes I see them fast enough to not have to re-do much of the work. Not this time. I had tied on to the front apron rod, gotten the tension even across the warp and woven the first several inches before I realized I had missed one dent in the reed.
If my warp threads were closer together I could have ignored this but not on this rug warp. My warp threads were set to only 4 per inch so I could easily see the offset. I had to tear out my weaving and fix it.
Fortunately, the error was close to the selvedge so I didn't have to tear out too much.