Blackcat, have you taken the mosin bolt apart to clean it. Or has the rifle always had this problem? It sounds like either you have a problem with the way the rounds are being presented to the face of the bolt as it is pushed forward. Or possibly short stroking the bolt.
If you load only one round the rifleseems to operate properly.
But when you want to load more than 1 round you have this problem.
When you use more than 1 round do you load with a stripperclip, that may solve the problem for you.