SBBS

Can anyone recommend a good repair center where I can take a 4Kw Axpert Inverter for repairs.
The Inverter just started to do continues resets when input power is connected, and if I disconnect all power from inverter (input and output), and only have battery power connected to inverter (although battery is fully charged), then the inverter switch off completely.

Yes, I think you've got it :-)
Lets use a simple example with just two inverters. Lets say one of the inverters is running at 3kw, but there is only 1.5kw solar coming in on the mppt of that inverter. Well, then it is going to use 1500w solar and 1500w battery. This will drop the voltage of the battery.
Now add the second inverter/mppt into the picture. If you also have 1.5kw solar coming in on this second inverter, and only a 500w load, then that inverter will push 1000W into the battery, attempting to lift the voltage of the battery.
Your net discharge on the battery is therefore only 500W and all the solar is being used.

Hi Wetkit. Thank you for your reply. I have already agreed in one of my previous posts that I must split up the solar panels per inverter will do that soonest. 
As far as the rest of the discussion is concern about the if I need to get more solar panels (or another inverter) ...... If it looks like I am confused, then I must admit I am confused.
Some of the previous people that posted comments say that the Inverter can not share a 3000 watt load on one inverter between solar and battery. And some other people had comment that it can share the solar and battery on the same inverter (if the load on a specific inverter is bigger than the solar capacity on that specific inverter). For the sake of not repeating the whole previous discussion in this comment to you, all I need to clarify is the following.
Question 1: If the inverter can share the load between solar and battery on the same inverter (if the load on a specific inverter is bigger than the solar capacity on that specific inverter) , then I do not need to get more solar panels.
Question 2: If the inverter can not share the load between solar and battery on the same inverter (if the load on a specific inverter is bigger than the solar capacity on that specific inverter) , and the other 2 phases need to keep the batteries charged then I do need to get more solar panels.
However, I will go with the comment that Viper_za had made (that it can) .... because it is what I want to hear ... lol... then I will not need to add more panels

Firstly I wan to thank Mart-mari for the information that she had posted. I also need some advise on this topic. I have a three phase installation with 3 x 4 Kilowatt Axpert inverters (in total 12 Kilowatt), but only use max +-5 kilowatt at any point in time over the three phases combined. I have 18 x 310 watt Yingli solar panels (total 5580Watt). I have done the installation myself as I have an electrical / electronic background, and have taken great care to comply to all Standards and regulations. I have also a COC certificate from a electrician that came and did inspection of everything after I have done the installation, and the electrician did all the connections necessary in the three phase DB board, ( i only did the Solar panel connection, battery connections and Inverter connections). Therefore I can say that almost all of the faults that Mart-Mari indicated is considered in my installation and as per requirements. However the one point that concern me is the point 1 in her list, that " solar connection between inverters must be completely seperate".
Does this mean that each inverter must have it own solar panels connected to it, and that you can not share the panels across all three  inverters. I have a connector box on the top of roof with the necessary fuses and surge protection, based on how I stringed the panels in series and then in parallel I have three cables coming into the connector box at 25,59 amps each. The fuses that I have used in the connector box is 30 amps. After the strings go through the fuses, it is bused together to combine all the strings in parallel to have 76.77 amps. I then have three separate 50 amp DC circuit breakers feeding each (of the three) inverter so that I can disconnect the solar power to any one (or all three inverters) should I need to. 
My question is this. If I have 76.77 amps connected across all three the 50 amp DC circuit breakers, and each inverter draw from the 76.77 amps what it needs, is this correct or do I need to have seperate solar panels for each inverter.