Try one or all of this:

(require 'dired+)                                                              
(setq diredp-bind-problematic-terminal-keys nil)
                   
(defun dired-custom()                                                          
  "conf dired-mode"                                                          
  (local-set-key (kbd "M-O") nil))                                             
(add-hook 'dired-mode-hook 'dired-custom)
     
(eval-after-load 'dired-mode '(define-key dired-mode-map (kbd "M-O") nil))

Try one or all of this:

(require 'dired+)                                                              
(setq diredp-bind-problematic-terminal-keys nil)
                   
(defun dired-custom()                                                          
  "conf dired-mode" 
  (diredp-toggle-find-file-reuse-dir t)                                           
  (local-set-key (kbd "M-O") nil))                                             
(add-hook 'dired-mode-hook 'dired-custom)
     
(eval-after-load 'dired-mode '(define-key dired-mode-map (kbd "M-O") nil))