Like others say, the truck's charger circuit is pretty weak.
And 30A for 15 seconds of slide operation is 0.125 Ah ??
But then there's the electric Tongue Jack, electric stab. jacks, electric awning. They all pretty much depend upon the batteries for operation. But they are also all short duration.
Best thing is to have a well charged, substantial battery bank.
Then you don't have to worry about it, especially with solar panels, or when plugged into 120V.