Usually external associated repairs such as isolators and power supply factors. Internal inverter repairs are often a sign the inverter is coming towards the end of its serviceable life, and continued, unrelated repair costs could be on the horizon.
Most inverters are comprised of layers of circuit boards affected by excessive heat during the energy conversion process. Over time, the heat breaks down the integrity of the delicate electrical components that can almost result in a domino effect of failure in a reduced period of time towards the end of inverters lifespan. A Bathtub curve aids in translating the end of serviceable life for inverter technology.