New equipment might be creating more RF noise.
Someone moving stuff around may have bumped something or moved wires around.
Hard to tell without lots more details, but here are some general rules:
- DO NOT put your router on anything warm
- DO NOT put your router where it gets direct sunlight
- DO NOT block the air vents, or encase it in a cabinet somewhere
- DO NOT let the data cables that go to it get near electrical power leads, power strips, wall-warts or anything like that
- IF you have to cross wires, do it perpendicular, and do not go parallel
- DO NOT run data and electrical wires together, distance is good, distance plus not in the same direction is better
- DO make sure the antennas (if any) are perpendicular to your expected wi-fi using locations. Do not POINT it at your device but point it at 90 degrees to where your device is
- DO NOT let the cat warm it's butt on the router, or let pet hair or anything else build up
- DO reset the router and cable modem periodically by removing electrical power for a few seconds
Chances are, the installer guy dropped the router right on top of a power strip with three wall warts on it and now you are getting messed up transmissions from it because it's too hot, or it's getting interference directly applied to the circuit board / cpu.