I do Subject interviews for folks going through a T-3 investigation all the time - but then I am in investigator.
I have seen triggers for many things over the years - some serious, some because the Subject omitted information, and a lot of humorous triggers from Subject’s who don’t read the questions before answering.
A Subject interview is basically your opportunity to provide information to the adjudicator through an investigator/agent. This is not something you want to buzz through quickly. For Tier 3 - something jiggled the system. Ensure you give the full story and all the information you know. A good (experienced) investigator will try to pry the full story out of you, the good, bad, and sometimes ugly, to include the why and what happened afterwards. Hiding information during these interviews don’t work out for you.
The Tier 3 process, unlike the old NACLC/ANACI allows the investigator to talk to other folks to figure out the whole story - so give your side during the Subject interview to the investigator.