Question for On-Cycle Interviewers

Question for those that interviewed candidates during on-cycle earlier this week:  

TLDR: What were some of the mistakes you noticed candidates making or reasons why you/the interviewing team dinged a candidate? How would you fix/change these mistakes or reasons why that candidate got dinged?

Apart from the obvious of missing a technical question that can be found in the guides or completely flunking a model test, what were some of the mistakes you noticed candidates making or reasons why you/the interviewing team dinged a candidate? Also, what would you do to fix/change these mistakes, and specifically, how would you prepare otherwise?

Examples: not making/defending reasonable assumptions they made during a model test, not being able to talk about the deals they completed during their summer, bad answers to behavioral questions, performing poorly during a case study, etc.