Monkeeee01
Retro Guru
I think you are right on the BB length as I used the one I bought specially for my old Middleburns which needed to be longer if I remember correctly.Crossing the cables means the inners are exiting the outers at an angle, increasing friction.
Best avoided if you're struggling to get a good shift.
I also wonder if your bb is too long - this puts the statistics too far out and affects the cable pull to movement.
I have the one I was using on my other Kula with this Curve chainset that is shorter and was set up by my LBS so I should swap them over!