@Jessica Booker might be able to tell you more about this, but I'd say that while it obviously isn't ideal (as it can show you have some difficulty with managing time under pressure) it is also definitely not a deal-braker for conversion chances. In one of my VIs I got cut off at the end and was still progressed to the next stage.
How detrimental the impact is I think will mostly depend on the overall cogency of the rest of your answer. If you are cut off just as you are finishing a concluding sentence after articulating a clear and structured response, I would expect the impact to be minimal. However, if you are cut off after panicking midway and not managing to finish the explanation of your main points, it might matter more.