When they go down into the basement Taylor says "Wow, that must be a Faraday cage," referring to a glass box around the computer equipment. But a Faraday cage must be made out of a conductive mesh, that's how it blocks electromagnetic fields.
From the beginning, Erin tells everybody how her ex is highly technical and hacks his way into her life to harass her. She expresses absolute certainty. Yet, she is shown to have expensive high tech smart devices for things like her thermostat and door locks. Having them instead of classic, non-smart locks and thermostat allows him to hack them to harass her, as she keeps reporting. She wouldn't spend so much money to have devices he can hack. If she got them while dating him, her fears should lead her to remove and replace them immediately.