Refrig ok , freezer not working properly

The refrig works fine, however the freezer side, warms up and then starts to freeze again. It will freeze a bowl of ice, but then starts to thaw out the ice , until the cycle starts over again…I just installed a new defrost timer, and it still does the same thing…The temp setting on the freezer side is max cold, and the refrig is in the middle…

I am pretty good at fixing things, and much dicussion we had here at work, we decided to "shotgun" the timer first…This is in my garage, and keeps the beer cold, but my wife needs the freezer side working properly!