I saw the source code and you are using one trail to draw all the lines on one side.

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=2564.0
Has An array to draw each lines seems pretty permanent to me.

Even more permanent is the analytical lines but loses some accuracy in the line plots.

Each method can some problem.
Array hangs the simulation sometimes especially when drag the view.
Analytical is not accurate but seems like the best thing moving forward, for the time being.