Could it be the Anti-halation layer sticking to the ridges and leaving streaks? When I use my homemade BTZS tubes, I have to remove the film and fix in a tray. If I don't I get streaks from the flim backs resting on the inside of the tubes.
I also have the 8X10 Unicolor tube. I can see the ridges running length wise. They would be touching the film base, not the emulsion.
Just a thought...