No solution to offer - just my moral support.
Annie was 4 mos and Joey 5 mos when they came to us. Used same crate and schedule training as our perfectly housebroken previous dogs (three sporting mix breeds) but it seemed much more difficult for the corgis and I had many moments of thinking they would never be housebroken. They will still have an occasional "accident" but I have a sneaky suspicion they are being vindictive and it's not an accident
.
We have a fenced yard but during the "process" always went out with them to make sure business was taken care of before play or returning inside.
Good luck and I'm sure Harley will "get it".
Paula
Annie & Joey ... he/she did it - not me!!
PS - no extra patience here.