I suspect the triac or an internal connection just went bad. I have had horrible luck with these Asian SSRs. The old ones we used seldom failed and when they did it was quiet, No melting, smoke or fire. The check sorters I worked on in a previous life had about 50 of them in each machine. Everything from 2a to 45a rated. The 2a failed a lot (small shaded pole motor) until they swapped them all for 10a units but it was a quiet failure. I am using them in my spa controller for an 11kw heater (two 5.5kw elements) and the pumps.
