Resist the urge to replace things first
When a smart home starts behaving unreliably, it is tempting to blame the newest or most visible device — the hub, the app, the last light switch that was added. I recommend not starting there. Check the weak links further down the chain first: power, network, and how the system was originally commissioned. Before I recommend replacing anything, I work through the same checklist, roughly from the ground up.
I'm deliberately not giving you specific test figures or pass/fail numbers here, because the right checks depend entirely on your installed system and your installer's commissioning records. What I can give you is the order I investigate in, so you (or whoever you call) spend less time guessing.
My diagnostic order
I move through these roughly in this order, because each layer can produce symptoms that look like a problem in the layer above it.
- Power stability: have there been recent power cuts, voltage dips, or work on the consumer unit? Controllers and gateways that don't reboot cleanly after a power event are a very common cause of 'random' faults.
- Physical connections: loose bus cabling, a damaged connector, or a device that's been knocked or re-terminated during other works.
- Network health: is the controller or gateway on a wired connection where it should be, and has anything changed recently on the router, switch or Wi-Fi — a firmware update, a new access point, a changed password?
- Device firmware and app versions: mismatched firmware between a controller and its peripherals after a partial update is a frequent, overlooked cause of inconsistent behaviour.
- Recent changes: has anyone added a device, renamed a scene, or had another contractor touch the system since it last worked reliably? The timeline is a useful first clue.
- Environmental interference: new wireless devices, baby monitors, or neighbouring networks can affect wireless control systems that previously worked fine.
- Commissioning records: does the original installer have programming notes, a device list, or an as-built schedule? Without this, every diagnosis takes longer than it should.
Why the network layer deserves special attention
A growing number of 'smart home' faults are really network faults wearing a lighting or climate-control disguise. If your automation controller, bridges, or IP-based lighting gateways sit on a congested or unmanaged home network, you will see exactly the symptoms people usually blame on the automation brand: slow responses, scenes that fire out of order, devices that drop offline overnight. I cover network separation properly in a companion article on building a more reliable automation network, but the short version is: isolate control-system traffic from general household Wi-Fi traffic wherever the hardware supports it, and keep critical controllers on a wired connection rather than Wi-Fi.
If your system integrates with network hardware such as Ubiquiti's UniFi range, their own documentation on network segmentation and virtual networks is a good general reference for understanding what proper separation looks like, even if the final configuration needs to be done by whoever manages your network [1].
What to record before you call anyone
The single biggest time-saver, whether you call me or another engineer, is a clear written account of the fault rather than a verbal 'it's just not working'.
- Exactly which scene, room or device is affected, and which ones are unaffected.
- When it started, and anything that changed around that time (power work, new devices, an app update, a house guest adjusting settings).
- Whether the fault is constant, time-based (e.g. only in the evening), or random.
- Whether a manual override at the physical switch or keypad still works, even when the automated version doesn't — this single fact massively narrows down where the fault lives.
When to call a qualified professional rather than self-diagnose further
Anything that involves opening an electrical enclosure, touching mains wiring, or working inside a distribution board must be left to a qualified, licensed electrician — this isn't a DIY step regardless of how confident the troubleshooting has gone so far. If the checklist above points to a device-level or programming fault rather than wiring, that's usually where I come in: reviewing the commissioning, checking the programming logic, and fixing the actual cause instead of swapping parts until something happens to work again.
