[RE-wrenches] Arcing from inside Trace DR2412

[Benn Kilburn]

Wrenches,
An off-gridded (system installed by others) called me yesterday with a concern. 

His system is older and has had mods added over the years. It is up to 7x Siemens SP75 and 1x She'll SQ80P. 

I believe the inverter is the original. It is a Trace DR2412, and where the concern stems from. 
He says he has noticed an arc from inside the inverter about 3 of the last 8 times he has fired up his generator (remote start next to inverter). He described seeing the arc thru the vent fins on the top right of the inverter. 

Is this internal arc typical when a generator connects to the inverter and he just hasn't noticed it before?

...or is his ol Trace toast?

Thanks,
benn
Sent from a 'smart' phone, with touch screen keys. Please excuse shortcuts and typos.