I used to have light dimmers in my house that worked just fine; but after an electrical panel upgrade they became erratic and/or noisy. All the dimmers are powering LEDs which claim to be dimmable and the dimmers claim to be LED-friendly. And this used to be true, before the panel upgrade.
The first one we noticed, and which we tried to show the electrician who did the panel work, would become flickery when the vacuum cleaner or the toaster oven were running (both on different circuits) but it would only do it sometimes and of course it never when he was looking; so he shrugged and said to just keep an eye on it. Eventually we gave up and removed the dimmer.
Another light started buzzing after the panel was upgraded, and we assumed the light was faulty and replaced it but the new one also buzzed, and I only realised the other day when I decided I didn't want a dimmer there that removing the dimmer fixed the light.
Other lights on dimmers struggle to start when they used to have no trouble starting at all.
I can't think what could happen at the panel that could make this sort of thing happen... or what other environmental factors might happen at around the same time