A common speculation in SF is that a true interstellar drive would not work deep in a solar system due to the gravity well or perhaps the solar wind - you might have to jump into or drop out of warp/supralight well away from the system core, perhaps out past the heliopause, then proceed in on sublight drives. There is some hard science evidence that reality may mirror fiction in this regard, so this could be the case here.
or it’s a big rock