We noticed this happen just before the transformer failed. We have Kichler under cabinet LED

Just a followup, in case this will ever help anyone else. It was the bulb! The pendant over the sink got worse. Sometimes that light wouldn't turn on, especially if it had been dimmed previously. Later, while the other lights on the circuit all remained steadily illuminated, it would suddenly go on. The down periods got more frequent and longer. Finally, I tried switching bulbs with the other fixture (yes, it would have been smart to try this earlier). The other bulb worked in the sink fixture, and the sink bulb didn't work in the other fixture. Eureka! I got a new bulb, at less than half the price I paid for these in 2011, and the light works fine now. Apparently, the bulb was going bad, but it took a long time to do it. Pretty annoying, since that LED bulb cost $33 and was supposed to last longer than three years.