Open Door Alarm

I have a freezer with an open door alarm that will not turn off. It is maintaining temperature and there is no ice build-up nor cold spot around the seal. As it was due for a defrost, I shut the machine down for 24 hours and dried it thoroughly to make certain there was no ice buildup inside the machine tripping the alarm. 3 minutes after turning the freezer back on the door alarmed again.

Since the freezer is maintaining temperature, it seems a bit unreasonable to pay a technician to come look at it. However, I don't want this to be my freezer that called wolf. I'd hate to lose so many samples just because I thought it was the dang door alarm again.

Is there something I can check/replace?