[rohrmann]

I'm wondering if you have a flow problem, and when the furnace is not running and your fridge is, everything is good. Then, at night, when the fridge may be off but your furnace may be on, then the fridge wants to run but there isn't enough gas volume available so the fridge locks out due to not enough gas. Just a wild guess, but I would suggest having the system checked if you don't find anything obvious.