When I interview, two things I always look for at as things to be concerned about are many short term (and not contract) jobs, and big inconsistencies between LinkedIn and their submitted CV.
This is of course on top of discussing their recent projects and seeing how far they can drill down into them.
I do this to weed out people who are very suave at interviewing, but turn out to be not only incompetent at the position, but actively poison the org. These folks are rare, but they do exist and can cause lots of organizational harm. They are aggressively self-promoting people who don’t know what they’re doing, but can fake it convincingly for awhile somehow, and who work energetically for higher and higher positions.
Often CV and LinkedIn are way out of whack because of the level of creative nonsense they have gone through about their pasts to get a job. I don’t mean this in the “CV is marketing you” sense, I mean this more as “saying you were CTO when you were a junior QA person” sense.
Many short stints can mean they were found out within a few months/year of being hired.
An odd variation on this is talking about very important sounding positions that turn out to be their own one-person consulting company.
In the past 5 years I have seen three cases of this where they were hired (2 I did not interview, 1 I did and was a “no”). All three imploded rather spectacularly.
I have also seen good candidates with bizarre CV inconsistencies or several short stints in a row who explained it all very sensibly and turned out to be great.
This is why these aren’t CV screening red flags, but points of discussion.