It appears that the source of the problem may have been an AC to 12VDC charger for a Lithium Ion battery that may not be completely isolated from the AC lines. The problem disappeared after disconnecting the charger and operating only from the battery. It is now running without problems from a good quality AC to 12VDC adapter that is properly isolated from the AC circuit. The Stellarmate is operating from a 12V to 5V converter with the goal of portable operation from a 12V battery only.
I apologize for exercising folks with an issue caused by my poor quality system. But at the least it has been an excellent learning experience for me and I hope this experience will save trouble for someone else interesting in setting up a portable system. Thanks for all the help in gaining a better understanding of the Stellarmate system and the Celestron equipment.