I'm no kind of expert in the brioche stitch. For example, I just learned the other day that what I was taught to call brioche 30+ years ago is actually a variant stitch called "half brioche." However, as a result of a very interesting discussion on Ravelry I did get to figure out how to drop a column in the genuine brioche stitch, and then latch it back up. This would be a way to fix brioche several rows down without having to un-knit the fabric stitch-by-stitch.
Rather than reproduce all that stuff here, may I direct you to the thread on Ravelry? Specifically of interest is a very good video (not mine) at post 27, as well as a photo-essay (by me) at post 34--both the video and the photo-essay show how to run out and re-latch the genuine brioche stitch.
Tangentially related is another series of posts (by me) in the same thread (posts 10 and 11) showing how to make half-brioche by dropping down a column in reverse stockinette fabric, then latching it back up. Of course, if you can make half brioche this way, you ought to be able to fix it that way. In short, posts 10 and 11 would be helpful if you're having trouble in half-brioche stitch, posts 27 and 34 would be helpful if you're having problems with the genuine brioche stitch.
Good knitting, TK
