Facing the exact same problem. Right after enabling the watch unlock, everything works. I step out and come back, either after a reboot or the computer goes to sleep or the watch goes out of range of the hack and it stops working. The hack definitely can connect to the watch as it prompts for the watch to unlock but the watch doesn't seem to respond properly. It is not just a matter of sleep. Everything else seems to work (air drop, side car, handoff) and I am using a tri-stream DW1830.
And no I don't have a serial port and don't have a corresponding BIOS option on my machine.
Anybody else got to the bottom of this problem?