heart rate monitor blitz

Recently my Polar heart rate monitors have been going beserk. I have a 700 series watch I use to check fitness and heart rate variability. Imagine my surprise when seeing the watch registering heart rates of anything from 190/ 224 /238 with the heart symbol flashing quicker than the eye could follow. At 78 years old you could say I was a little worried. However since I was not having convulsions or blacked out I checked at my wrist, it seemed normal. To check I used two other polar monitors, 100  and 200 cs, same result. I swapped chest straps of all three against each other, same result. This has occurred a few times lately, surely there has to be local interference. A further check whilst this was ongoing using my Garmin 25 and another gps watch with hr monitors indicated normal as at my wrist, low fifties. I contacted Polar for a possible explanation informing them of recent LED street lighting installations. I know from experience that a flashing led light alongside a bar mounted hr monitor sends it wonky but any help they could offer may answer my concerns. Other than to say their latest bluetooth offerings may be of benefit no explanation for possible interference was forthcoming. I can only assume that someone locally is using high frequency equipment. Anyone else out there had similar experience, the polar monitors work as normal most of the time but why they should go beserk at times is beyond me. During time trials and other energetic progammes I am a ‘high beater’ averaging during a ten between 174 /178 bpm with around 52/54 resting heart rate when recovered.