Angie,

 

It's sad, but true!  Your service representative was correct about resolving the icing problem when he said you should defrost your cryostat regularly. 

 

The primary function of the nightly defrost on most of the new cryostats is to melt the ice that accumulates on the cooling coils.  The resulting water is supposed to drip into a catch pan and then be evacuated from the freezing chamber through connected tubing.  This sounds easy, but the water will create those unique (and irritating) formations in the chamber if the tubing becomes disconnected or plugged with debris, if the water in the tubing refreezes before the evacuation is complete, or if the pan has been damaged so the water doesn't run toward the tubing.  This problem will be exacerbated if the unit is used heavily, especially in a high humidity area.

 

If you can defrost your unit once a month you will probably see an improvement, plus it will also give you a great opportunity to thoroughly disinfect.  Be sure to dry all of the moving parts and then lubricate them with the oil that is recommended by the manufacturer.