the rate should be positive. hold of that for a few days, I believe I added a bug some where on the joint contraptions, that is making the joint unstable. yes if the tow object go to sleep, changing the actuator do not wake them up.
But I am covering too many things at once, I decide to complete the scaling stuff before I figured out what it was that cause problem with joints.
Take your time. I think next month we're going to do a game jam, and the theme will be machines people can make with this new functionality. It's really great.