I have this same problem with my iMac. If i power off my hx stomp whilst it is connected to the computer it boots my keyboard and mouse off too?? I have to manually restart my mac using the power button in order to get my mouse and keyboard back? SOOOOOOO annoying!
First time it happened i lost loads of work :(
Has anyone fixed this issue yet? Im running the latest firmware, installed the latest driver for Catalina and am not using a usb hub or anything, just straight into the main usb port.