You need to clean your stepper units, especially the pivot points. If you take the pivots apart, be aware there’s a nut on the back that has to come off before you can unscrew the bolt. Oftentimes, that bolt will still break, so be prepared to order new shoulder bolts from PB Resource.

Try just using isopropyl alcohol to clean the pivot before taking it apart. The steppers should move crisply and quickly when the unit is clean.