Hi Rachael,
Towelhorse here, before my condition improved, I used to get the zingers all the time. They would happen most often in the evening and I could easily make them happen by wiping down the dining table. I believe they were occurring due to pec minor syndrome, as the day wore on and I lost scapular stability, the pec minor would become dominant and crush the brachial plexus. Any use of my arm away from my body would cause the electric shocks. I used to be a telecommunications technician, I worked with telex machines which operated on 50 volts and 100 volts DC. These Pec minor zingers felt to be well over 50 volts. The source of the zinger would vary sometimes, if I straightened my arm my elbow would pop. I reckon this was because I was putting tension on the nerves down my arm (as well as crushing) and trapping the nerve in my elbow. If I was you I would try and avoid making the zingers happen, the frequent crushing of the nerves will make your hand less useful and you will be further from the path to recovery. Regards Towelhorse