2019 NX300h... I've noticed in the last month, the lane assist lines are now gone. With cruise control on, I do see the 1/2/3 bars for following distance, but the parallel vertical lines, showing the cameras see the lane markers, are not there. I did check in settings, and the lane assistance guidance, or what ever that is called, is turned on.

 

You probably have but -- did you try resetting it -- turning off and back on?

I have not had this problem but I copied and pasted your statement with 2019 NX300h into Google and came up with this -- maybe this will help...

 

I know how to steer, so it didn’t render the car unusable by any means, but I found it odd. The option is still in the settings and turned on, but didn’t have it all during the drive. Anyone else experience this before? Just curious mostly.

 

Besides in the LTA settings in the centre screen you can also (de-)activate the Lane Keep Assist / Lane Trace Assist with the button on the steering wheel. I deactivated it by mistake once and I noticed because the vertical lines were gone.

 

The steering wheel button is the quick and easy way to disable the LTA when driving
on roads with markings that confuse the system such as construction zones. I have
found that sometimes "crack fill" tar strips that crisscross the traffic lane will also confuse
the camera.
The more elaborate menu that you should customize when parked lets you turn off the
"Lane center" feature that tugs the wheel or change the alert from the wheel shake to a
chime. (I call the two alerts, "twitch and bitch") because of the motion and sound.

 

Recently noticed that when driving on the freeway with well marked lanes, in Cruise Control, the car self steers, staying in its lane. If changing lanes, the cruise control picks up the new lanes and continues steering by itself.