Sunfish has found the same thing. Here is one of our typical system’s inverters over 4 years. This is with the Enphase in Business! We don’t sell Enphase micro inverters anymore. We switched to string, wall mount inverters. We have had no string inverter failures since the switch almost 3 years ago. If you are frustrated with your micro inverters Sunfish can switch you out for a reasonable price. The switch will end up saving you your money back in service calls and increased efficiency. String inverters are now running up to almost 98% efficient!
Enphase Micro inverter 4 year failure rates.
Why you should not go with micro inverters for your solar power system
Source: Sullivan Solar Power Blog | Dangers of Micro Inverters