I have the same wiring and same problem. It works fine when I connect load directly to the switch in 2-way (doing this for now so I can turn on the lights). Once I connect the two non-common wires from the dumb switch to the traveler and load on the smart switch and common on the dumb switch to the lights it stops working. I switched to 3-way + dumb using the button code mentioned. When I revert all the wiring back to the same previously working 2-way configuration and switch to the single pole mode with the buttons it no longer works. I have to factory reset to get single pole working again. I just started a new topic on this issue before seeing this topic.