have got a loose screw
To be or seem particularly silly, eccentric, crazy, or mentally unstable. (Also written as "have got a screw loose.") That guy on the corner has definitely got a loose screw because he's been standing out there yelling obscenities at passersby all morning. My old Uncle Pete has got a few loose screws, but he's a really nice guy. What's the matter with you? Have you got a loose screw, or what?
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.