CSV Import updating Quote Lines

I have a sales order that I need to update the lines for. I have MANY lines so I would like to use a CSV import. I am using multiple files with the first file containing the internal ID and the second file containing all the lines. Since I have multiple lines with the same item ID, I tried to map the line ID, but when I do this, I get the following error: "The record has been deleted since you retrieved it." This is whether or not I choose to overwrite sublists.

If I don't map the line id, I get the error: "This record contains duplicated key or keys. Please correct it before next update." I assume this is because I have multiple lines with the item "TBD", which is an temporary item we use until we have the final item number assigned.