I have an 898 si and I'm having trouble when I'm en route to a waypoint and I mark structure on the sonar or the sideview and mark it with the cursor and hit go to it won't stop navigation to the previous waypoint and when I try to cancel navigation it tells me the waypoint is part of a route and I can't stop navigation. The only way I can stop it is to go to the chart page and hit skip next waypoint. Is this normal or is my unit malfunctioning ? Thanks