This has been reported previously but it has not yet been addressed: Trails do not properly show up when the trail emitting part is offscreen - #7 by CoastalStarlight
When the part that carries a trail goes offscreen, it stops rendering.
The video below shows that the trail does not render whenever it is out of the camera in my game. The Pink part is the route that the trail’s part has traveled.
Here is a simple repro file that demonstrates the issue:
TrailBugRepro.rbxl (53.3 KB)
Expected behavior
The trail should render even if the part that carries it is out of the viewport.