Nu har jag typ provat med
@RestControllerAdvice
public class ExceptionHandler extends ResponseEntityExceptionHandler {
    @Override
    protected ResponseEntity<Object> handleExceptionInternal(java.lang.Exception e, Object body, HttpHeaders headers, HttpStatus status, WebRequest request) {
        if (e instanceof HttpMessageNotReadableException && e.getCause() instanceof JsonParseException) {
            return ResponseEntity.status(HttpStatus.UNPROCESSABLE_ENTITY).build();
        }
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(handleAll(e));
    }
}