CO detector /fridge

[Baursculpt]

1965 caravel. The original gas only fridge works fine but sets off CO alarms. I have two in trailer and both activate when fridge is running. The flame is blue, I blew out orifice, cleaned the chimney with 3/4" wire brush and checked the venting, it's clean and open. I'm stumped, any idea what the source of CO is?

[TG Twinkie]

If it is one like I had in my '69 Shasta. There is a flip down door below the refer door. Which opens to the interior of the coach. It is not air tight. Those old refers were not designed like the new ones.
This is the same era where we had standing pilots on the cook stove and oven.
Do you have those pilots lit?