Black hair dye... need I say more? LOL

I`m new here so first I`d like to say hi to everyone! I need a little advice. My hair is very long and curly. The natural color is very dark brown with red highlights. Well a couple times every year I dye my hair black to freshen up the color a bit from the sun fading my natural color. I`ve never had a problem before, the black usually fades after about a week and I have a nice really dark brown color with red tones. Well I used a different brand this time, Clairol Hydrience, because it is really gentle. I used soft black. It totally grabbed jet black and some spots were not even and it hardly faded at all. So I waited about 5 weeks and attempted to redo it to even out the color. For some strange reason about 2 inches of hair starting at my scalp turned a medium reddish brown color. So now I have light roots and the rest is black. This was about 6 months ago. So now the roots are really driving me crazy and every month I attempt to correct them with black yet it won`t cover this medium reddish hair for anything. It`s been about 6 weeks since I`ve done anything to it. I was hoping the black would fade more so I could just put a dark brown dye on all of it. No such luck. Now I have very dark brown roots starting to show, then about 2 inches of medium reddish brown and the rest is jet black lol. Luckily it`s not very noticeable unless I am under very bright lights but I`d like to correct this w/o having color correctors put in it as I don`t want dried out damaged hair on top of it all. I bought some protein filler at Sally`s to use before the next coloring. Should I just try dyeing it all black again and hope it evens out or should I use dark brown and hope it lightens the black up a little bit? I`m not about to get it bleached out and I have tried Prell which only made my hair very dry for a couple days. I can live with black hair since it`s so close to my own color, I just want it even!
Thanks for any suggestions!