Hi Chrisikins,

I am aware about the "bug"...

I don't really consider it a bug because I did that intentionally (so that the rest of the code can work properly)

I actually rarely use the underscore "_" when I make my programs, I just don't like it...

In your case, you can write your code like this:
Code:
HeaderString = "item-name" & Chr(9)
HeaderString = HeaderString & "item-description" & Chr(9)
HeaderString = HeaderString & "listing-id" & Chr(9)
HeaderString = HeaderString & "seller-sku" & Chr(9)
...
I was planning to fix the "bug", but I always forgot about it, and I rarely have time latelly to look over the code to fix the problem.

I don't understand why would it remove the "_" in only some cases... maybe if you post the code before and after change by my Add-In... maybe I can figure out why this happens...