At times my sub zero 561 fridge side will go from of temp 32 to 42 is this normal?

No, it's not normal! Sub Zero prides themselves in their refrigerators that keep an even temperature and last for a long time. That said, I had one with similar issues. It wouldn't keep the food cold.

After calling repair services twice (the first one didn't have any idea what he was doing), I called the company. They were very accommodating and in the end, bought the unit back from me.

Don't be afraid to call them and explain the issues. They can give you the name of a repair service who knows the product and is reputable. If it isn't repairable, they may help you out, too.

The most common reasons for that problem are: (1) Dirty coils inside and out on that model, and (2) the thermostat's spring tension has changed over time and the differential has changed. Since it is going so low it sounds like the thermostat could be to blame. You can get a universal thermostat, but I would get an exact replacement for that one because of the difference in the way Sub-Zero makes their units. Here is a manual: https://dl.dropboxusercontent.com/u/8010163/Sub-Zero_500_series_refrigerator_b.pdf
If your coils are dirty, clean them well with soap and a water hose nozzle and make sure to clean the fan blades. You can remove the fan blades to clean it right by unscrewing one nut on the motor shaft on most units. Keep water out of the fan motor, but oil it. You should be able to fix it very easily as most are easy to work on.