malfunctioning accessory dimmer switch

I just moved into a home that has a RadioRA system, and it all seems to be working fine except for one accessory dimmer switch that behaves strangely. The main dimmer switch will turn the light on and off and dim it as expected, and the light it controls works fine with the remote keypad too. But the accessory dimmer switch (model RA-AD) will turn the light ON if it is off but will not turn the light OFF if it is on. Additionally, when I turn the light on using the accessory dimmer switch, it comes on at the lowest brightness setting and steps up one level in brightness every time I press the accessory switch; can't turn it back off using the accessory switch.

I thought the accessory dimmer switch might be bad, so I bought a new one from eBay and replaced it, and am getting the exact same behavior. Any ideas what is wrong here? Is the accessory dimmer wired incorrectly? Is the main dimmer switch bad? Is something messed up in the central repeater? Or is this just hopeless and I should resign myself to having a non-functional switch until I want to replace the whole system?

Appreciate any thoughts here.

Hello! We apologize for the issues you're running into. It is possible that there may be a wiring, bulb compatibility issues (if using LEDs), or a Radio RA issue. We would advise emailing in to systemsupport@lutron.com or calling a live agent at 1-888-Lutron1 (588-7661).