I encountered a fog problem with new Delta 400 120; there's overall mottled fog with heavier fog down the center of the film.(posted 8548 days ago)Process and camera problems have been eliminated as the cause; I think Ilford's having a QC problem.
Speculation.....
Another roll of Delta 400 that wasn't loaded into a camera, just taken out of the package and processed, is ok, no fog.
The camera that two fogged test rolls were shot in puts a fair amount of pressure on the film and rolls the 120 rolls rather tightly, somewhat more than the usual Hasselblad, Mamiya etc back. It doesn't fog HP5+, Delta 100, old Delta 400, Delta 3200, TMX etc.
We had some problems several years ago with old Delta 400 in a Noblex; that camera puts some severe bends in the film plus there's lot of drag (pressure against rollers) when the film is wound. Symptoms were foggy streaks in the direction of film travel. Other films were ok.
So....I _suspect_ new Delta 400 _may_ be excessively sensitive to pressure and/or bending. I'll shortly be sending the fogged test rolls off to Ilford to see what they have to say about it.
I doubt there's a problem with your camera or process.