Good morning,
I couldn’t find a Carter Hoffmann W323s manual, but they do have a lot of modular warming cabinets for a variety of uses. That said, the low temperature alarm means something is faulty and will need replacing.
It’s either the heating element, a relay, an air probe, or a controller on your unit. My guess without seeing the unit would be it’s not the heating element, since you said the top is still keeping temperature.
Perhaps another user has more insight. I hope this helps a bit!
John