Don't know why the tail is so long...
I use git found the problem.
I dragged the Line2D and somehow change the scale, and that's what happened.
I will leave the post just in case someone has same issue.
So hard to find and driving me crazy....
CHECK YOU LINE2D'S SCALE
I am just getting to this and wanted to say thanks a lot for sharing your answer. I'm glad you could figure it out too!
It will certainly be helpful if someone else has the same issue in the future.