The T5/AC puck is doing the job, it just needs the time to work a bit more. I prefer a triple pass over that style puck. First pass removes most of the green (leaving reds behind). Second pass reds usually go away for me, leaving an amber tincture. Third pass takes it to nearly water clear. The red you are seeing is not oxidization; it is leftover pigments or tannins from the plant. AC should help.
Maybe read up on the lostbiologist’s SOP. I scaled his a bit and have had nothing but stellar results.
Are you making distillate or just mixing your crude with terps? Distillation can have issues when filtration media is left behind. That usually translates to isomerization, though, and not necessarily color change. The dry ice is also likely making your tincture rather acidic. Ethanol loves to pull carbonic acid from dry ice.