After weaving quite a few inches into the towel I thought something looked off and discovered I was missing a thread!
If you find the pin in the picture you can see that part of the pattern just looks a bit off. Follow that line up to where the thread finally is threaded and you can see where the pattern got corrected after I added a new warp thread.
@kyle
In northern Sweden you can almost always find one error in old weaves, but no mistakes. To make a perfect weave was considered prideful.
In case anyone new to weaving is wondering how you recover from a mistake like this, measure out a new warp thread, thread it through the reed and heddle, and then hang it off of the back of the loom with a weight. I wrap the end of the warp around the weight until it hangs properly, and unwind it a bit every few times I advance the warp.
Then wrap the other end around a pin and pin it to the fabric. After enough rows eventually tension will keep it in place.