When I am connected to shore power my two inverters are overheating, why?
Little more detail would be good.
Ambient temp / how is the location of inverters ventilated / are inverter internal fans running or are they disabled with silent assistant ? / what charge or load are they doing.
How have you determined they are overheating? They should derate the hotter they get.
Also check, if the heat may originate from a bad contactor / connection point down the wiring. If there is a high resistance contact somewhere, that could produce a significant amount of heat and distribute back through copper wiring easily.
Especially if both inverters are overheating at the same time, this may be the case.