Single Step sometimes restarts the evaluation

[tbelaire]

When I click on single step, it sometimes resends the laser pulse from the emitter instead of continuing the existing one.

You can see that here, as you can see the 'trail' of the old pulse 3 steps in, as well as the new laser pulse.

You can see

[filipchudzynski]

The same problem happens when one use pause, play button interchangeably.