Kitchen Aid Wine Chiller Not Cooling

Hello,

I have searched the old questions and can’t find the exact one I have. I have an older KitchenAid Wine Chiller that has stopped cooling. Both fans and the condenser are running when turned on and turn off and on using the thermostat knob. I have replaced the thermostat once before with a part from here and help from this blog.

My question is. Could the defrost timer be out or is it more likely an problem with the sealed system?
I don’t mind buying one and trying before trashing this expensive unit.

Thanks for any help.