I foound myself with a mysterious band that I cannot remove. I exited the client gracefully after which I saved the log.txt. I then restarted the client, the band was gone. It was also not present in the saved copy.
The log:
log.txt
I don't think that's band, it looks like a "pull vector".
I haven't seen it recently, but there was a issue where the pull vector would stay behind after you released whatever you were pulling on. It used to happen a lot, and I seem to recall it was a problem back in the days of the 32-bit Windows client.
I think that some stray click or key press while pulling caused the problem, but I was never able to recreate it.
The ghost pull vector didn't do anything, but there was no way to get rid of it without a restart.