In CS17 class, I was trying to use the debugger to "figure out what went wrong" in a recursive function where the recursive argument was not being decremented. I pressed play to jump to the error (Stack Overflow) and then pressed the step back button. It caused a fatal error. Pressing the ok in the dialog did not terminate the application. I had to force quit it. (The event number in the debugger window was around 64,000.)
I was running Camelia with Cygwin (over ssh) and with Exceed.
The code I was working with was
let rec summorial = function
| 0 -> 0
| n -> n + summorial n - 1;;