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Here is my situation:

I have two interviews for the same firm, different office, but same interviewers. One I was preselected for and the other was assigned by lottery. What is customary here? I don't want to take a slot away from someone else and I also don't want the interviewers to think ill about me for having two timeslots. They are also nearly back to back (there is one interview in between). I would ideally like to be at the office that preselected me but I wouldn't mind the other office.

Drop the second office and just tell the interviewers the first time you're interested in both. What would be the point of interviewing twice with the same people? Unless you wanted to prolong your screener and answer double the questions, but... why?

Is it true that if you were assigned by lottery as opposed to a pre-select, that you are less likely to receive a callback?
This is assuming that because the firm doesn't want you in the first place.