Check your PO's for 0 conversion factors.  I don't think the problem you had with losing and reloadingpart numbers would be a factor, I believe that if the item PO Conversion factor is a 0, the PO will automatically make it a 1.
 
As for correcting it, you can make a type P adjustment at IN-C but check - if the PO Receipt already posted to the GL, you don't want to post to GL again so you will need to delete the GL entries from the adjustment.