PO invoicing giving an error

I have a  sales order and intercompany PO sales order got invoiced but even i try to invoice it gives an error 

item :123

Transaction has already been posted.

I have debugged the code and found that 

error comes from :

[s] \Classes\SysDictClass\invokeStaticMethodIL 51

from 

 // Transition to IL and set the system date since sessions do not get current session date time by default
        result = runAs(
            //BP Deviation Documented
            curUserId(),
            classNum(SysDictClass),
            staticMethodStr(SysDictClass, invokeStaticMethod),
            [_className, _methodName, _params, true, DateTimeUtil::getSystemDateTime()]);

I have did full CIL but still I am getting the same error and the issue seems with the particular purchase  order.

any clue or help will be appreciated