Did you modify the form or is it printing that way with the standard out of the box form?

I modified the form for other things, but nothing to deal with aliases. So I guess I would say out of the box.

I assumed that if you could enter the alias number in the item key and have it select the Sage item key, that it would just use the alias entered and not all that may apply to that item key.

Also under the "Alias Item Numbers" help it says this, "...The system detects that this is an alias item. If you are unsure of the vendor's part number, click the Alias Item button in the Item Code field to display all general alias item numbers and any alias item numbers that are established for this vendor."

I do not see an "Alias Item button" in the Item Code field.

If you linked in another table, instead of having the Wrk table as the only data source, that is the most common cause of duplicated rows. The work table should not have multiple rows of data for the same order line, and you could confirm that by Previewing the report and leaving the Preview open while using DFDM to check the temp table data.
Aliases only help with data entry, and are not stored as the Item Code in the order.
In Item Maintenance, or on the PO Entry's Lines tab, the flashlight button shows you your alias listing.

The Alias Item Number and Alias Description are both stored on each line, in fact you can see them in the secondary grid in Purchase Order Entry. The Alias number you select/enter at the Item Code field is stored here. The Wrk table actually contains by default the VendorAliasItemNo. If you join this field to the IM_AliasItem table instead of the Item Code, I would expect the duplicates to go away (assuming that this is a table linking issue).

I do indeed have the Wrk ItemCode linked to IM_AliasItem. I switched the link and it works great now. Thank you!