Recently had a user issue where an invoice journal was created in Dynamixs AX 2012 and attempted to post, failed-(possible system crash), generated a new sequential Invoice Journal which did post successfully; however, the XML generated that is captured by our Accounts Receivable department was the original INV#. Once I found the table in the AOT I was able to find the sequential database Record ID gap. Is this an issue stemming from the process of our AR software capturing an XML at the wrong point during AX invoice schedule posting or do we have a Dynamics AX issue?
Probably the software capturing the XML. If you create two journals (1 & 2), then delete 1, you'll probably have a gap in the RecId sequence because you deleted it.
It sounds like the software capturing the XML is not a valid atomic process, and it received something in-progress.
Keep in mind this is all totally a guess based on the information you provided.