My guess is that the flour has not been allowed to absorb enough water giving you a sticky dough that is difficult to handle. Also, the gluten structure may be insufficient. Wet dough needs either more time or more kneading. My general Santos routine using starter culture:
1. Pour water into mixer bowl
2. Dissolve salt into water
3. Dump in 80% of flour and mix with rubber spatula until all flour is wet
4. Let rest 20 minutes
5. With fork turning, add starter culture
6. Sprinkle in remaining flour
7. Knead for ~3 minutes. You'll have to do this enough times until you recognize when the dough is just right. Time will be different for each batch. Although it may be counter-intuitive, for Neapolitan-style dough, less is better than more. But just right is best.
8. Allow dough to rest for 20 minutes.
9. Run the mixer for a few turns of the bowl.
11. Bulk ferment