That shouldn't happen? Normally, the button is grayed out while optimization is running, but after it converges or reaches the max number of steps, you can change the parameters and restart. You may want to lower the max number of steps when trying things out. Sorry if it's a bit clunky!
I'm seeing the same thing: after it converges, there is a pause of a second or two, and then it starts again, making it impossible to set the number of parameters. On Chrome, mobile.
