Kindly help to confirm whether you encounter the following situation 1 or situation 2, and then follow the solution.Situation 1:Both single pole dimmer switches are turned off, turning on the switch will turn on another dimmer switch, or adjusting the brightness of switch A, the bulbs connected to switch B will be turned on or flicker. But when both switches are turned on, they all can work fine.Situation 2:Both single pole dimmer switches are turned off, turning on the switch will turn on another dimmer switch, or adjusting the brightness of switch A, the bulbs connected to switch B will be turned on or flicker. And when both switches are turned on, adjusting the brightness of switch A will change the brightness of switch B or let switch B flicker.For situation 1, you can replace the single pole dimmer switch with the 3-way dimmer switch DS02 or replace the bulbs.For situation 2, the only solution is to replace the bulbs.