How to fix "One of the selected pulleys is already fixed" error in belt/chain mate ?

when I gave the very first belt/chain mate then there was no problem.but as soon as I gave the second belt/chain mate a bunch of warning and errors popped up. showing "no solution found". and after the belt/chain mate ,it is described that "One of the selected pulleys is already fixed".

What is the possible cause of this?
I am uploading the zip file.problem is in the file named "conveyor".