Are you able to monitor the unit in any way to see what the internal temperature sensor is saying prior to fault?
I notice the temperature of my PIP clone rises to its highest overnight with very little load. It sits about 7-10°C higher than during daytime when it's working. My daytime loads are typically not high though, <10% of inverter's (4kW) capacity.
This is what my solar output typically looks like over a regular 24-hour period with reasonable sun during the day:
View attachment 85594
View attachment 85595
Load is mostly a pool pump and a few sundry electronics running 24x7.
When the solar first starts producing in the morning, the reported inverter temperature drops quickly. I suspect something about the solar PV starting production triggers the internal fan to operate. It also tends to be triggered by applied load. As load is increased the fan steps up its speed. With no/very little load the fan seems to barely operate.
IOW the fan doesn't just seem to be controlled by temperature sensor but seems to have various triggers.
Perhaps the cabinet needs some active ventilation to help dissipate heat? These inverters are supposed to have plenty of space around them.
One thing with my PIP inverter, and I understand it is reasonably common with these inverter types, is the fans are mounted in a direction to draw air in the through the top vents and blow it out the bottom vent. I never understood why it would do that. Makes more sense to me for them to draw air in from below and blow it out the top, the same direction natural convection would operate.
It is possible to turn the fans around but that would require opening up and modifying the inverter and presumably void whatever warranty you might have.