Item status error in process

HI Experts,

We are in SRM 7.0 classic scenario we are facing issue with shopping cart in " Error in transmission " status,item status is "error in process "

for non catalog shopping carts with preferred vendor .

Error in RZ20 for the shopping cart is " Enter Vendor "

Even though it is Non-catalog SC it is trying to create PO at back end and as the vendor not there Back end throwing error.

There is no issue in SRM customization.

Please provide youe valuable inputs how to check and rectify this problem.

Thank you!!

Regards,

Bhargava A