Inverter problem, over and over

I've had a 3000+ watt inverter for about 3 years and it goes out repeatedly.  Control board, AC Board, transformer, etc.  I have everthing up to code and everything the manufacturer wants, but including surge protection and the largest wire sizes possible.  It just keeps breaking.

My system has two arrays. 
1, with 22, pvl-136s and
1, with 18 pvl-144s.
2, 80 amp charge controllers and rigged for float coordination.
Charging 8, Trojan L-16H-ACs @ 435AH.

The batterys connected to 2, inverters thru the appropriate breakers.

I have 2 inverters used one at a time....one 1500 watt for low wattage for heavy clouds or very cold temperatures.  The small one draw much less power.

The bigger one, very high end and expensive goes out and goes out.  The smaller one, an Aims industrial has lasted 6 years and doesn't quit.  I used it in the beginning to build my house, but found that when it's below freezing outside, it draws much less power and keeps the battery voltage higher.

The more expensive one is thoroughly grounded and protected in every way, going into my load center, and it breaks all the time.  The smaller Aims is completely undergrounded and only uses extension cords on the floor.  It never breaks.

Never had an issue with the charge controllers at all, just the one, very expensive inverter.

Any ideas or comments welcome.