The problem is the screws in the side have stripped out of the holes. Put in some toothpicks, or other wood and wood glue. Then push the fridge
in, screw it down, and you are done.
What ever you do, don't run it like that.
On edit: Since it is a Burro
, the kitchen is made of fibreglass, so it may be a better idea to take out the fridge
, glue some 1x1 wood around the hole on the inside of the cabinet. When the glue drys, put the fridge
back in and screw into the wood that you added. This will spread out the load, so that this doesn't happen again.