Red Flags on a 'Paid Test Day' for Crew Hires?

Hey everyone, I'm Sarah Chen, a cinematographer focusing on commercials and narrative work. I've been fortunate to work with great teams, often with trusted referrals. But I'm currently crewing up for a mid-tier commercial project (shooting on an ALEXA Mini LF with Orbiters and SkyPanels) and trying to expand my network beyond my usual circle. I recently brought on a couple of ACs recommended based on their rates being very competitive. I did a quick 'paid test day' for a product shot, just a simple setup, mostly to see their workflow and attitude. The shoot itself was fine, but I got a weird vibe. The general advice is always 'don't hire the cheapest without vetting,' which resonates. My question is, beyond obvious things like showing up late or general incompetence with an ALEXA or my Fujinon Premistas, what specific, subtle red flags should I be looking for during a paid test day to identify someone who might be a bad hire long-term, even if they can technically do the job? I want to avoid issues that end up costing more down the line.