Might be worth figuring out if its a screen drawing issue or something else.
It does seem to be related to the process involved with the stations being built. It doesn't occur before that point.
Might be related to :
Spawning process
Unhandled collisions exceptions
Game over criteria (if it exists)
Some kind of variable out of bounds issue
Screen drawing priority
I didn't test for different browser's behavior. I was on Chrome.
Hope you can figure out what the issue was. Its a decent idea for a game.