loose seal used upright freezer

Recently bought a used upright freezer and noticed that the door seal is coming loose from the door a little and also from the freezer. When the door is first shut it seems to seal and then it come loose after a second or two. We are wondering if you have any advicefor this problem. I have read on line that you really need to replace the whole door and then other sites say you can replace the seal. We might as well have bought a new freezer for the cost to replace the door.
Thanks
Terrie

tcarlson762
The first thing I would do check the door frame for the rust. If it’s rusted just dump the freezer and buy a new one. If it looks good and you would like to replace the door gasket, the part number for the new one is AP2113453
For the references here is the break down diagram for the Frigidaire freezer Model FFU20F9GW3
Gene.