line (debug line or trace line by channel) disappeared sometimes

hi there
I wanted to draw a line in forward of my actor. I can do it with draw debug line and line trace by channel. but it just visible in some special view and when I rotate my camera around actor, disappeared suddenly. (when I change the view again, appeared.)
I got really confused!
notice that I have really large environment (about 100 km* 100 km). could it be the reason?

how can I see this line(trace line) always?

This is 5.3, right?

There’s a problem with line trace visibility at the moment.