Do you see any bubbles, nodes on the string of the material? The diameter of the material should be 1,75 mm and the surface of the string should be consistently smooth without irregularity. If possible, please attach a photo of the problematic spool of Z-ABS blue you have.
It will help me to diagnose the problem here.
BTW, have you cleaned the nozzle? Did you try to load the material without the nozzle mounted?
I'm not sure if I understood you correctly. Do you mean that while loading the material, the sprocket wheel starts to skip, however it caeases after a while.
Am I correct?
If so, please demount the nozzle and load the material without it. Let's see if it has any effect on the process of extrusion.