There is a problem when a decisor works in a second iteration with an index counter

XOR gateways cannot have multiple incoming flows.  It will work fine the first time but any subsequent attempt will fail to complete the XOR node, exactly as what you're seeing here.  The standard recommended best practice is that if multiple flows come before a single XOR gateway, to merge those flows prior to the gateway by feeding them into an empty Script Task (i usually name these "Merge" for consistency, but it can be anything you want).

Yeah, i have put an empty scriptTask before the decisor and it works :) 

Yeah, i have put an empty scriptTask before the decisor and it works :)