The gasket that seals the door of my freezer failed to keep the cold inside the freezing chamber.
The result was poor freezing, frequent ice crystals formation near the door and wasted electricity.
Investigating the problem I discovered that the gasket had flattened at some places and wasn't flexible any longer.
Thus it didn't quite meet the freezer's lip and created a hole from where the cold could escape. Or equivalently, the warmth could slip in ;-).
Step 1: Grab Some Aero-stop Tape
I used some aero-stop tape to cushion the gasket where it meets the freezer lips.
This stuff is used at doors, windows etc to insulate any slits or holes that allow heat/cold to escape. It easily cut using scissors.
I encircled the lips of the freezer.
Step 2: Done!
Now the freezer works flawlessly. Fortunately there was no need to replace the gasket.