I doubt its a bug. One possibility is you are using Copy and at the “point to move to” prompt you click multiple times in the same location. That will create multiple copies. With Rhino for Windows sequence with Copy is left click on object to be copied, right click for Enter to complete picking objects, left click on location to copy from, left click once on each location to copy to, right click for Enter to complete the command. If I left click rather than right click when I want to complete the command a new copy is created with each spurious left click.
Another possibility iff you used Gumball to create or manipulate the curve then something in your sequence of gumball actions may be generating the copies. I’m not a Gumball user so I can’t help with any specific suggestions.