In my opinion there are three different kind of possible failures for a solar inverter:
1) Infant mortality due to poor assembly work or components intrinsic defects. In this case the solar inverter lasts for few hours or days before to fail
2) Wear out of components like fans, electrolytic capacitors which lead to a "natural death"
3) Unexpected real world conditions (bad grid voltage quality, bad installation, interaction with other devices on the same grid) which can lead to hardware failures or loss of production due to unnecessary alarms tripping. In my experience this last kind of failure is the REAL failure any manufacturer fear and try to avoid.
For example I've been investigating a lot about unnecessary alarms tripping on solar inverters which were developed in Taiwan and used here in Europe. The Taiwanese design was flawed by the kind of electric distribution used in Taiwan, resembling very much the American style power distribution: almost every building is fed by a dedicated medium voltage to low voltage transformer. This ensures a clean and strong grid. But in Europe the power distribution is totally different. We have big central medium to low voltage transformers serving tens of users together. In these conditions equipment can interact with each other even in different properties. After all the conducted EMI compliance takes into account the frequency range 150kHz - 30MHz but a lot of interactions can still happen below 150kHz.