First of all, capacity reduction of the main circuit electrolytic capacitor is probable.
Usually, the electrolytic capacitor is replaced every 5 years on average, however, if the inverter is used at a high temperature and under a load close to 100%, the capacity reduces faster.
Capacity reduction of the main circuit electrolytic capacitor results in increase of the output current, leading to OC2.
Check if the output current has increased using the current monitor of the inverter or an ammeter. If it has increased, contact Mitsubishi FA Center for inspection and replacement of the inverter parts.
However, if the increase of the output current is rapid, the load may have the cause of OC2. Thus, check the load again.