He suspected EMF interference so as a quick first step he decided to throw together an EMF detector using an Arduino.

emf detector 3 Articles Measuring Electromagnetic Fields With Just An Arduino And A Piece Of Wire April 17, 2022 by Robin Kearey 9 Comments ...

A total of 10 I/O pins (D2–D11) of the Arduino UNO is used to drive a 10-LED bar graph display (LDA-B10ZX). Here, the bar graph is wired to digital pins of the Arduino through 470R current-limiting ...