I've had 3 GFCIs fail.

1. Leviton from the 1980s: tripped randomly, even on the bench

2. A different brand, plug in type, made in Korea: triac
exploded, power stayed disconnected

3. Factory replacement for #2, very different internal
design: failed in 10 days in the opposite way -- power
stayed connected, test button had no effect.

The replacement for #3 has worked fine for over a decade.