7 months in, ready to give up

[Stella and Zoey]

I have 2 cats who I started on the LK system in the fall. They started off well. We did the cardboard method and were great. Got up to amber, no cardboard and was great for a while then one cat started pooping on the floor. During the cardboard phase, I ordered the multi cats ring to help with the green transition.

Once stella started pooing on the floor, I went down to the small amber ring. Kept the girls there for weeks without accident. Went to full amber and all was fine. I then went away for the holidays. While my brother was cat sitting, stella went back to floor pooping. We started back at ground zero. This time we got up to multi cat green. All was GREAT for 11 days then stella went back to the floor. We then went back to multi cat amber and she was fine. Moved back to Amber a few weeks later and she's back to pooping on the floor. I am frustrated and not sure the headaches are worth it. Not sure what I'm doing wrong. I am ready to quit. I know it takes some cats a year to learn to use the toilet, but after 7 months, I'm at my witts end. I am going to go back to RED for the last time... but this is it