From the look of your negatives it appears that you have the same problem I had with Paterson reels some time ago. I know you have washed your reels, but my problem went away after I washed and scrubbed my reels and tanks in hot water and regular washing-up liquid.
It is not a camera problem as the density is lower and extends into the edge markings. It is not a coating defect as far as I can see. My only guess would be as Bill said earlier about bubbles or my idea that it may be the reels, but I have no idea. I would have gone with the bubble theory, but the marks are so large. Sorry.
This may be a longshot but I once mixed developer in container that was thoroughly washed and cleaned but once contained ethylene glycol. Apparently the chemical leached out of the plastic and contaminated the developer in such a way that it caused striations across the film that were about 1/2" long and separated by about 1/2". They looked like long versions of your problem.
I got some brown glass jugs and have never seen the problem again.
I would mix a fresh batch of developer in case something strange got tossed in when you prepared the developer, perhaps an oily substance got into the developer and floats to the top and sticks to the film, preventing development.