Just built my first fly rod a four piece and was really happy but now noticed a rough defect on the side of one of the ferrule wraps can I shave that blemish and re epoxy or will that cause more problems?

Yes, you can trim it off, lightly sand the wrap finish with 220 of finer sandpaper and apply a light coat of finish over the wrap. The old finish won't adhere well after 24 hrs without roughing the first coat. If you don't use fine sandpaper you'll see scratches under your final coat.

thanks for the help

I had to do that on a decorative wrap that did not flatten out well. But I found that I had to go all the way to 400 grit paper to completely remove any scratches that would be visible.