Recently I bought via ebay auto extension tube #2 for Mamiya RB.
Yesterday, when I first time try to attach it to camera I found that I can`t close the security ring of the tube-to-lens side to attach lens to tube. Finally after numbers of attempts I could close it a little, but after I release the button it doesn`t lift the mirror all the way, but just move it a little bit. Did anybody encounter the same problem?