Gen 2 Hybrid Battery: Still error after replacement of one bad cell

I did similar swap in ‘05 Prius recently; it also is showing errors afterwards!

 

The Reaktor works on only one 8V cell/module at a time. It completely drains-recharges-drains-recharges, etc the module individually. It is what I used to test, and then recondition the modules that I found healthy from the donor battery I had bought.
You recondition the module by doing at least 3 complete deep discharge and recharging cycles on it, with the appropriate wait times inserted between them, of course. If the module then tests well, I consider it healthy and a good candidate for transplanting.

Your issue with pumping 7500mAhr energy into it and getting only 3000 out of it is a common thing and a bit of a red herring. The energy going in isn't the important thing, it is the energy that the module can put out afterwards that is. Often the charger will go on stuffing current in there till the cows come home while the module just cooks off the overfill in heat. If the output is only 3000 and decreasing after each charging, then that indicates the module is weak. Find one with a capacity that more matches the ones already in your battery. Healthier modules will have steadier, or improving discharge capacities as they are treated.

Not all chargers have automatic programming options. My Reaktor had limited automation, such as cut-off voltages, charging rates, time-outs, and wait times between cycling, so it requires a bit of attention to do it properly.

The Prolong does for your entire battery what the Reaktor does for the one individual module, only it does it for all 28 of them at once. It is less targeted, and thus not useful for rehabing failing modules, which need to be identified, and physically replaced with healthy ones.
Once the battery is repaired, Prolong can help keep your battery healthier over the long run, by deep discharging all modules and dissolving the internal crystalizations that build up, and balancing the top voltage levels.