The min speed for the Handy is different depending on upstroke or downstroke. For downstroke, somewhere betwwen 30 and 40 units/s. For upstroke, somewhere between 20 and 30. I usually keep actions above 35 when scripting.
https://discuss.eroscripts.com/t/the-handy-working-at-slow-speeds-a-scientific-video-study/109466