My wife and I have also experienced this issue. We submitted it to the support staff, and their reply was that they hadn't seen it happen to more than a couple people, but they'd forward it onto the QA team.
We have a screenshot similar to yours showing that we had -99 consecutive overhits.
Supposedly if you complete the quest but don't impress the NPC, you will get two random Icarus weapon parts and some spices. If you impress them a little you will get five random Icarus weapon parts and some spice. I have only done that once.
I have heard that if you really impress them you get an Icarus weapon recipe, but with the quest in the state that it's in, I've never managed it.