The inverter/charger only has a 16.6ms delay, but it will switch back to inverter power if the voltage is too low or too high, or if the 8A internal AC fuse is blown. My guess is that the voltage dropped too low and it went back to inverter mode and before it could cut the DC output for being too high it blew the reverse polarity fuses from the high amp draw. (A 1400W AC draw is about 130A DC on my setup).
I wired my transfer switches in after the breaker box, 1 15A transfer relay for each 15A general circuit. This leaves the a/c, converter, fridge, and microwave on shore power only.
If your wiring allows you could do the same with the circuits you want to have inverter power on, then only the gen/shore can power the things like the charger, a/c, and microwave.
Instead of feeding the inverter/charger with the main input I would put it on it's own 15A breaker. Then the output would connect to 1 or 2 circuits in the camper with the high use items.