Vase mode not working

[sonesh]

I've been trying Vase mode (its called something else outside of Slic3r) for a few days now, to print a single perimeter object with a single stream of filament, however the X and Y are working fine, but the Z axis doesn't move up. I can see the axis trying to turn, but it keeps bouncing back. After a minute, there should be a noticeable height on the print, but its still there printing at ground level.

I have no issues with printing normally at 0.1mm height, but it seems this tiny but constant height increase is too much for the Pro B.

Has anyone had any success doing this? At the moment, I'm thinking either the stepper drivers aren't up to the job, or the motor can't do movements that small.