Retraction Causing Skipping
Fighting stringing will not work by increasing the temperature of the hotend.

There could be 2 possible causes for your problem, 


the first is that you still have a too high retraction speed, too high for your stepper to follow (do note that the default value in Ultimaker Cura is 25&nbsp;mm/s),
the second is that you retract too far and the cooled "hot" filament tip is deformed and causes extra tension/friction in the extruded liner.