PC Db Br403

Hi, i've managed to couple two BR403's together but now i'm unable to uncouple them even when i press uncouple button, any advises?

 

At least in the BR423/425 you have to hold the uncouple button for 5 seconds.

 

I tried that, but nothing happened.

 

I tried "local decoupling" from the driver's manual as closely as possible as the regular procedure doesn't have the required menus in the MFD's, but no luck either.