1. Check if the batteries are connected. (If your robot powers off right away as you switch off, the batteries-for UPS- are not working at all), and it might cause you mastering loss on powering them off.
2. Small robots are quite vulnerable to external forces when they are powered off especially vibrations. You might need to rectify the environment if that's your case.
3. Losing mastering while they're being powered sounds not really good. Could be considerably incorrect mass data of your attached tool that's affecting high and sudden external torques when releasing breaks(if it is, your robots will fall down quickly a bit downward or up when you hold enabling switch and start any kind of motion manually, and the axis that lost mastering will be the ones that are mainly lifting mass of your tool-2,4 usually-), or your robots actually have issues.
