I feel I found the problem, but if others have had this issue, I would appreciate confirmation. After 15 minutes the emi interference really started and I even turned the sensitivity down, went back to the front of the school where I had smooth threshold before and it made no difference. Went to two other locations-same thing. Did the reset, took out batteries and ran fingers to rotate them in case they were loose. Finally, I finger tightened the connector. No change. Then I noticed the connector would still move, so I tightened with pliars and everything turned smooth. Went to a park famous at times for emi, cranked up the sensitivity, and everything still rock solid smooth. After 30 minutes returned home. Hope it's fixed.