Cable Winder problems

When the system is working the edges of the reel are unbalanced according with the center of it. I improve the system using an algorithm to increase or decrease the point of return for the traverse according with the dancer behavior. The PLC is Allen Bradley SLC 5/04 and there is no way to know the exact position of the edges of the reel. The system uses an encoder with a 1746-HSCE2 module in an extension rack.
Any ideas?

Thanks