I never double coat VDB when using Stonehenge. My paper is from the old mill and I understand the newer stuff is different and many do not like it.
I agree the streaks have to do with fingerprints.
Your exposure times seem excessive. Are your negatives that dense or is your printing frame too far from the UV source? Tests as spelled out in the Post Factory Journal indicate that with UV fluorescent tubes essentially no separation between the frame and the tubes is necessary. Mine are approximately 1/2" and do not produce banding.