Transit tube build planner issue

I'm fiddling with transit tubes.

This is hard to explain. I go into the construction planner and I click on the transit tube.

The second image is as things are normally.

I can fairly reliably achieve the state shown in the first image (no ghosted tube outline), by holding down "w" and "s" to move up and down (the game is paused if that matters). After a while the ghosted image just goes away for a while and eventually comes back if I move around more.

I have a lot of intermittent graphics glitches on my machine but this one feels like logic, because it's easier to reproduce and it tends to happen in the same places.

I'm calling it a graphics bug because I'm stupid and might be wrong about it being game logic.