Hi there l'm no expert but surely the major flaw here is that each camera uses film.
Each film would therefore in its own class, even though its the exact same spec, there will surely be very slight differences.
Each exposure will be subject to the quirks of the glass used
Therefore you'd get the banding seen.
I still think it's pretty the banding could probably be dealt with using software - but l like the previous poster's advice, using just one camera reduces differences between exposures because the glass and film roll are a constant, across each exposure. Even if there are animals moving about, you can stitch them all together. Maybe create a family of precisely cloned ponies at a watering hole, just from one pony lol.
If only vignetting could be eradicated