I also have this problem of not being able to remove them. Makes it hard to properly see the route.
Never saw those. Does it also alert you when you are getting close to them? I guess it beeps, like "before" sharp turns? Probably causing even more harm by disrupting your alertness exactly at the time when you should look at the road, and not looking at the screen trying to figure out why it beeps?
I don't know how but the alerts are gone now??