Something I've been curious about with the reduced agitation of C-41 development compared to B&W process, is bromide drag not an issue with color film and chemistry?
Actually it can be. I replenish my DIY c-41 'flexicolour clone' developer with the basic formula less the bromide and carbonate. None the less, the bromide and iodide does build up as more filsm are processed, and agitation remains important.
I see the effects of halogen reterded development around sprocket holes in 35mm films first. I try to limit myself to 1L of replenisher into 1L of original mix, to keep the halogen levels to tolerable limits. .
I've seen this in commercial labs occasionally also - nasty blue streaking around sprocket holes and next to transitions between unexposed and exposed parts of the film