Usually a switch works or it doesn't. Sometimes they can become intermittent, but to cause one light fixture out of three to flash seems very improbable. It does sound like each fixture is controlled by one switch? At a minimum, I would substitute a different light where the flashing unit is.

Mike; I guess I wasn't clear and I should have also given more detail on my question. No, all three lights are controlled by the same three way (or four way?) circuit. The reason I question switch quality is because I have read elsewhere about some flashing of leds in higher or lower resistance conditions. The reasoning wasn't clear.

Are your bulbs marked as dimmable, or non-dimmable? My experience with non-dimmable LED bulbs has been that most of them exhibit that kind of behaviour (cycling on and off or flashing stoboscopically) as they age. When you think about it, the electronics inside the bulbs that drive the LED's can't tell the difference between a bad waveform from a dimmer's triac driving the lamp, a bad waveform created by other electronics, or a bad waveform from a surge on the AC line.

I have never had this problem with dimmable LED's. I also found that many LED bulbs from big box stores, dimmable or not, tend to not last as long as the ones from electical supply stores. I have had good success with Standard brand LED's, but I am sure other brands will do just fine as well, expect to pay between $ 6-8 PER bulb.

The bulb on my mother's rear porch was installed 6.5 years ago and has never been turned off, at least not before she sold the house last June.

Note that these things are usually retrofits for Low Voltage (12V) Halogen bulbs. Even with no dimmer involved the cheaper ones of these can start to flicker. A cheap solution is sometimes to just stick one regular halogen bulb in one of the fixtures which seems to calm things down. Alternatively, by better LED bulbs.

wOlley: I don't think these are dimmable so I suppose your theory has some merit. Unfortunately, these are not bulbs, they are complete units including a plate of leds.

Which is one of many reasons why I will never buy a fixture where you can't replace just the bulbs

Anecdotally, I've heard that flashing LEDs like this are a sign of overheating.

I hadn't heard anything about heat weed, but it seemed like a possibility to me, so when the first one started flashing, I put some spacers between the base and diffuser to dissipate some heat but it didn't do any good. I suppose by that time that the damage had already been done. I didn't try it on the other units before possible damage.