Replaced clogged bird-mouth gasket with p-trap tube drain. How-to video very clear and gave me confidence to persist against stubborn hold-down clip at foot of drain that needed to come out. Bird-mouth gasket was clogged with dust and hairball. While I had the back off, vacuumed tons of dust out of the compartment (I should do that more often). Most time was spent reshimming the fridge at the end of the job when I put it back up against the wall and had to balance the door swings.