This problem is almost certainly one to do with Input Capacitance differences with different inverters. When companies build products they do not use the same components in every production run. They source parts and if they can get the same value part of roughly the same quality for a cheaper price they will buy several hundred or thousands of them for the next production run. Sometimes parts are not available anywhere (Like what is happening now). In these cases they will buy a supply from just about anyone who has something in stock.
I realize that SS really has no clue about capacitors so they keep on ignoring some obvious facts that all electronic engineers already know,
When it comes to Electrolytic Capacitors there is a large tolerance value between each cap that comes off the assembly line.
A good Capacitor may have a +/- Tolerance of 20% and a cheap one of the same uf value may be 30-50% or more of variance.
So a good Panasonic or Rubycon Capacitor of lets say 1000uf @100V will have a real value of anywhere from 800uf to 1200uf.
If you get an Inverter that has 12 of these in parallel and lets say that Batch average out at 850uf each, it would mean your bank value is 10,200uf.
Another Inverter may get a batch of twelve and the average value is 1150uf which would me it's bank value is 13,800uf. That is almost a 40% difference in the input capacitance between two inveters on the assembly line. And this is assuming the company is willing to spend the money for high end capacitor and trust me it may sound cheap when you price each component but it adds up when your building a PCB with a hundred or more components.
Panasonic Cap Specs and Price
