How should you run a useful business speed test?
Test from the location where problems occur, then compare it with a wired test near the router. Run it again during the busiest part of the day. One excellent result does not establish reliability.
Why can Wi-Fi and wired results differ?
Walls, distance, interference, channel use and client devices affect Wi-Fi independently of the carrier circuit. A large gap between wired and wireless results usually points toward the internal wireless environment.