This one tops the list for a reason. Keys get passed around between shifts, contractors, and staff, so it’s easy for one to go missing. And once it’s gone, you can’t be sure who has it. That’s a real security risk, not just an inconvenience.How to prevent it: Set up a simple key sign-out log. Or better yet, switch to keyless entry, so you can shut off a lost credential in seconds instead of rekeying the whole building.