LED bulb Q.

I had two out of four LED ceiling panels fail about 30 months into a three year guarantee; reduced light and staying on for 2 seconds after switching off. The drivers do contain two capacitors and a transformer; the replacement panel surrounds have extra ventilation.

The WiFi/Smart switch. is probably a semiconductor switch. It's probably leaking. And will fail .

I assume by WiFi switch you mean Tuya, Sonos, or similar? ( Whatever actual app you use on you phone, somewhere there is a ‘server’ which uses one of the ‘common’ systems.)

It isn’t unknown, although it is rare, for these to ‘have a moment’. I’m not sure how many switches etc we have, 15 perhaps. I’ve seen the odd stray ‘flicker’ of a light. I suspect other things have ‘flickered’ but not been noticed. One reason I’m dubious about using them on things where this could be an issue.

All of which may be true. And none of which explains why only one of the bulbs in the parallel circuit was flashing.

I would have considered the switch (hence my mentioning it). However as I say only one specific bulb did the flash thing.

I am vaguely reminded of how our fluorescent tubes in my parents house would faintly flicker in the very dark. Reminding us we lived very close to a power line and a high power radar installation.

Tolerances. That one hogs all the (very low) current that there is

It's adversary activated spy control protocol. Keep a watch on post hypnosis activity and behaviour of subjects, and ask your nearest to monitor and shoot you, just in case you were the one programmed.

Some "Neutral-less wired" Wifi Switches are made deliberately leaky, to provide a flow of current to the internal gubbins that make the WiFi work. There probably also is a long run of switch wire connecting to it, which is another leaky connection due to the total capacitance there.

Some LED bulbs are designed with SMPS type circuits, having a reservoir capacitor that just needs to charge to a certain voltage before the LED does its thing.