Con

What you have is known as a floating earth, which can cause a lot of strange problems, susch as getting shocked by the water in your taps.

I also had that issue, and solved it by having an Earth Spike installed (10 metres from any bulding) and have a 16mm Earth copper cable run directly to the inverters external earting terminal (lower right side). 

Another thing to double check is that there is no possible problem being caused by the reversal of the live and neutral feed going to the DB board from the inverter.

Under normal circumstances, the Neutral and Ground should be almost the same voltage with referrence to the live feed. This is what result from a municipal Earth-Neutral common feed. You need to make your own Earth-Neutral bond.