I have been getting these streaks on my color negatives. They are visible in the sky, on a wall or in any negative space. My process is as follows: I have been using Kodak Flexicolor chemistry. I use the sous vide method with a stainless steel 500ml tank. I put 435ml of developer in the tank, bring it to temp and drop the reel into the heated developer with the lights off, then put on the lid, switch on the light and agitate according to the Kodak Flexicolor instructions for small tank developing (1st 30 seconds, then 2 inversions every 15s). I agitate by inverting with a slight rotation, also according to Kodak. These are Kodak Portra 120 negatives, shot on a Mamiya RZ67, scanned at home. The issue is not in the scan, it is visible on the light table. My only thought is insufficient agitation or not enough developer in the tank? Pardon the edits, just wanted to make the streaks visible. Thanks everyone!