I'm not sure I understand the question? did it SHED after you shut the generator off and the system returned to shore power? If so, this may be normal.
On my unit: I have 30 amp shore power service. I can usually run both A/C units, but I can't run any other high power appliances if both of the A/C compressors are running, as the ECC will SHED one of them. I have an 11.5k btu in the front, and a 9k btu in the rear.
I have a short article that explains how the 120 volts is applied during shore power, and when the generator is running.
Rear A/C unit can be run on separate 20 amp shore power circuit – 1999 Southwind 35S