I can't be the first knitter who's done it:
And I know I'm not the first knitter who's had that problem either. What problem, you ask? You probably have already seen it. Yes, that line, right above the fancy cables where the simple cables go up into the sleeve cap. That. That is a dyelot mismatch.
When I bought the yarn, I bought so much of it (20 skeins) that some of it could have been a different dyelot. Before making this sweater, I checked all the yarn skeins, looking at dyelot numbers to be sure they were all the same. Two skeins (maybe 3) had no dyelot printed on them.
One of them was definitely the same dyelot anyway, and has been fully used. I thought I checked them all, but apparently I either missed one or in the light I was using at the time, couldn't tell. Now I have to rip and reknit, and it's really annoying because this was the last piece and I won't have the ability to block it for another week or so. I was really hoping to finish it sooner than that!