Okay I just found out the solution because during the countless amount of time trying the puzzle, I thought I needed to get the extra cat from the last chamber and not the second to last.
And the discussion about 11,20 must have been deleted because not one time in the comments was 11,20 mentioned, trust me, I looked.
That's unfortunate it was deleted - it actually had the step-by-step buried a few replies in. But glad you figured it out. The pointer about using the second last splitter chamber would have been the next tip if I knew how far you'd gotten - didn't want to give away too much too fast. That tripped me up for a long time too. I spent way too much time trying to copy the cat in the last part as well, only to eventually notice the other flag had one more move.
Won't be the last time you'll be stuck for ages and suddenly realize the solution that's only obvious in hindsight. Pretty sure Ethan could take over the world if he weren't busy making puzzle games. 🤣
