One-change diagnostic

Why does Wi-Fi fall apart in this room?

Weak beside the node is a different problem from strong beside the node but weak across a wall. Busy-hour failure is different again. Separate them before replacing everything.

Your result

Change one thing at a time

Separate room signal, node backhaul, placement, barriers, band behavior, and busy-hour congestion before buying more hardware.

Retest the same way

Use the same device, location, service, and approximate time after each change. A speed-test number is less useful than knowing which single move actually fixed the path.

Google's current mesh-test guide separates a weak point-to-router connection from room coverage and recommends moving points away from dense walls, furniture, and appliances. Use your system's own diagnostics when available.