Calss C motorhome - On board ONAN generator

My class c has a transfer switch and once when i was plugged in to shore power I started my gen. When I went to unplug from shore my transfer switch got stuck to shore power. I tried for a few day to get it unstuck and could not get it to switch back to gen power. Then all of sudden one day it worked.

I heard that transfer switches can stuck sometimes but i don't know if me being plugged in to shore at the same time had anything to do with it sticking. I don't do it any more, since then i always unplug first. Better safe then sorry.