My RS has been running fine since February 2019 but recently may have developed a serious problem or so it appears. Swarm would show occasional short bursts of the problem then the problem would kick-in for maybe an hour or so. Right now it sees the problem for over 4 hours continuously. Actual detections are there but heavily masked by this interference.
The problem or noise seemed like it could be the power supply but I swapped in a new supply today and there was no change.
In then next week or so I plan to try another RPI and also temporarily relocate it to another part of the house so I can work on it. Also I am using a passive POE cable so when I move it :to the bench", I will not use that.
Maybe the RPI be the cause? (Trying another RPI should eliminate that possibility.)
Maybe the A/B board has an issue?
Could it be some other external device in the house? (Moving it temporarily to another part of the house may help eliminate that possibility.)