Brendan was EXACTLY who I thought of when I watched it, but the same thought as you. Brendan was clearly led and otherwise answered truthfully. I couldn't compare the two instances because with Brendan they were molding him to answer the way they wanted (needed) him to whereas with Isaac, he was given free reign.
I really hope this is solved and it sounds like they're close. The second PI seems to be heading closer to home with his interviews. We'll see.