"White balance cannot be set" how to get a darker film border for setting white balance?

I’ve had this issue occasionally where the border of the film is scanned in too bright/dense, where Lightroom can’t read it as a neutral area to set the white balance from. I’m scanning using an Epson v600 and using Vuescan for RAW negatives. Is there any thing to adjust in Lightroom or Vuescan to fix this?

Bump. Dealing with this as well!