If you look at the back of your freezer, you will find a block of ice is covering the drain to the condensate pan. So each time the unit goes into defrost, the water created has no where to drain to except down the air passages to the fresh food section. Clear out as much ice as you can, and remove the rear panel from the freezer. At the bottom is the drain opening (you may need to do some searching). Clear this out with some hot water to melt the ice, and keep doing this unit water begins to run into the pan under the unit. Dry everything off, reinstall the panel and you should be good.

Unless you are having cooling issues, I wouldn't replace it. Just make sure the drain is clear. I use a 1/4" water line to fish down until I can see the other end in the pan below. It only takes a something small to start water backing up and eventually freezing to cause this problem. By clearing the tube, you are less likely of having a repeat failure.

Glad I could help.