Hi. Can anyone please help. I have 2 x 12Kw 3P inverters in parallel. The internal breaker keeps tripping randomly. If I look at the graphs, I can see that when this happens the current goes into minus. This is the only common issue I can see. It is set to zero export and this happens even at night when the total load is 500 watt. Any ideas please

Probably a damaged cable somewhere. Causes a short circuit or live to ground. hard to find especially if it doesn't trip the breaker or happens randomly. 

I had this fault and it was a damaged wire to the outside lights. It happens sometimes if it rains or windy the wires touch ever so slightly and trips or nothing happens. Nightmare to find it.