I have gone thru several starters.
From different vendors?
Fuel injector timing a mere few degrees too early can be compared to the Ford Model T.
The driver forgets to RHEEEEEE-TARRRRD the spark and when he spins the crank handle the engine coughs and tosses him over the trunk. I dealt with this a lot when customers complained of battery or starter problems. A Cummins for instance can draw 1,000+ amps if the PT injector pump is mis-timed.
Take the Genny-Rack to a genuine diesel guru who REBUILDS INJECTOR PUMPS. Yes they exist and yes they are back logged many times. My GM 6.2 diesel only drew 310 amps, at around 60F. Your generac figures are absurdly high.