Slow improvised asw ships like tugs (and even Flower Corvettes sometimes) do sometimes "blow their own tails off" when dropping DCs to shallow depths
and sometimes even sink, this is a known issue..happens more often in rough seas I've found
as to the CTD, I don't know what caused that....although ships exploding and all the graphic mayhem associated with sinking in combination with camera switches might cause it, I'd not worry too much unless it keeps ocurring..