Frigidaire Upright Freezer

Model: GLFU2067FW3
Serial: WB64137497

I'm not sure about the cubic feet but this should be close enough. I'm a service contractor but not a Frigidaire authorized service contractor. Anyways, I have a upright freezer with a Deluxe Temperature Control. The freezer is located in a garage. The set point is set at 0 degrees. From time to time it goes into alarm and flashes the temp of the case and the letter "E". It appears that the case is holding temp during the alarm. You can reset the alarm but the display still flashes the temp and "E". If you rasie the set point and let it go overnight the flashing will stop. After that you can set it back to 0 degrees again and it will run fine for a couple of days. The membrane control on the front of the door has already been replaced by another service contractor. I assume the "E" stands for some type of error. The freezer has also been known for not maintaining the proper temp, with water dripping out the bottom of the door. Where is the temp sensor located in the case? How does this wireless Deluxe Temperature Control work? What is the defrost schedule for this freezer? How does it initiate and terminate defrost cycles? What are the ambient temperature limits for this freezer? Thanks.