Aye, it happens to me whether I've tagged/disabled a flagship or not. Just this morning, in fact, I was kicked off the helm as I was approaching a Phantom and I hadn't gone anywhere near a flag. I haven't been able to discern any pattern to it, so have no idea how to prevent it from happening.
Although it takes only a few seconds to step away and back, I've had any number of close calls because of this quirk. So far, I've avoided sinking -- though yesterday I
just managed to regain the wheel as a Kingfisher was firing at me. Thank goodness for "Ramming Speed"!