Defrost drain hole line clog

Two years ago, my mother had a defrost drain hole clog in her fridge.

http://www.applianceblog.com/mainfor...tml#post114180

Had it repaired.

The problem is back. Beneath the vegetable crisper bins there is water building up and turning to ice.

I thought this was a fixable problem that would not come back? Why are we having problems again?

Can the refrigerator still run efficiently with this problem or should she invest in a new refrigerator?