Thats crazy
So how much is shoulderlength?
If i/we were looking at the back of your head, is it like 1/2 of your head? From the top of your ears and down is APL, and everything on up is SL?
Something has to be giving that part of your hair extra stress if its splitting and breaking off as a reason to why its not getting any longer......
Do you think its exposed more? The APL part of your hair might be covered on the top half with your shoulderlength hair if you wear it in a bun, and the bottom part of the APL hair is in the bun, so it might be completly protected.....and then your shoulderlength hair which is the top part of your bun is exposed to the air & gets dry more, maybe more brushing & combing to get it neat, and maybe your ponytail holder meets at about the end of your shoulderlength hair?.....
Also....when you shampoo, is that wear you usually put all of the product? I know i do that. I take some shampoo, put it in my hands, and start from my hairline & go down so the top part always gets lots of shampoo and the bottom barely any, i also cleanse my scalp with the shampoo more at the front section of my hair, not the back as much so it gets more manipulation. If thats the case maybe the shampoo is too strong/drying.
You might be using water that is too hot when you wash & condition and it effects that part of your hair more
How many months have you been trying to correct this? I see/think you joined in August- but your an old member right? ( i think i read in the fine hair thread someone welcomming you back)....but anyway, if you always had problems with the front part not retaingin length, sometimes it takes a couple of months to correct the problem, and sometimes hair doesnt show damage untill later, and splits are tricky aslo
I really have no clue, just trying to throw some ideas out there, i hope any of these might be a reason & your hair can get right on track....
How many inches apart is your shoulderlength & APL? I have layers and when it gets to APL, one section will be SL in the front, and one APL in the back just like you. Mine are 4" apart.