The E6 first developer is a high solvent, high acutance developer with special ingredients to promote good interimage, edge effects and stability. Many brands other than Fuji and Kodak do not use the same chemistry and suffer from a host of minor faults in the above characteristics. Some are severe and some are minor. All exist unless the exact method in the Kodak/Fuji formulas is followed.
This includes a balance of pH, bromide and iodide as well as the use of Hydroquinone monosulfonate for proper development. If these are not used properly, development in the many layers is not correct.
As for bleach then fix and blix processing, the blix for films is less stable and tends to allow for retained silver. A team of us spent over a year trying to develop a good blix for E6 and C41 and failed to do the job to our satisfaction although it yielded a lot of novel work and one patent. At present, I'm still trying to design a good blix and I now have one formula that works. It is not all that stable, but it works as well as can be expected when mixing an oxidant and a reductant.
So, be careful and beware of blixes used for color film processing. I have read several threads discussing retained silver problems from such processes.