Hi,Welcome to Just Answer, My name isXXXXX will be helping you with your appliance issue today.
The most common problem for this noise is the damper assembly, this is inside the refrigerator section behind the food,GE has had to redesigned these I have replaced many of them, that noise you hear the thump is going to be the damper flap assembly, which eventually is going to break, when this happens things will start freezing in your refrigerator section and it is going to happen, this is what GE writes about the new damper assembly,
Refrigerator air inlet cover/damper kit with fan motor. Damper and fan assembly have been updated to prevent freezing in the refrigerator. The fluttering you hear is the fan motor in the groaning is the damper motor opening and closing and like I said the thump is it snaps shut sometimes making a thump noise, this is going to break so you need to have them come back and replace it, they may tell you that your refrigerator has the new damper assembly in it but it's unlikely, they have used the original ones is much as they can to get rid of them, so even if this is new it's got the old damper assembly, get then the come back and replace the damper assembly, thanks and well wishes, Bryan