Hi, I myself stutter with words starting with “d” and many others. The social gathering thing happens to me as well. At one moment I am speaking perfectly fine, and when I’m asked to repeat, then I start to stutter. I think the main reason for that is that all the attention has been turned on me, and that triggers my social anxiety. Just what I think. I believe taking a few moments before repeating generally helps. If not, I just try to phrase the sentence in a different way I’m comfortable with. This happens to me not just in a social gathering but while talking to a person (mostly stranger). I’m not a professional in the field of fixing stuttering, I’m just sharing what I’ve experienced and used in my day to day tasks. Hope this helps. 😊 ✌️