FYI - I recently figured a way around the Add-on problem. I bought 1 add-on item along with multiple items from amazon pantry. The purchase generated two order numbers - one for regular amazon items and one for amazon pantry orders. I cancelled the amazon pantry order and the add-on order was unaffected and arrived in two days.
What I'm realizing now is after doing this 4 times and now wanting to use my pantry shipping credits which I had, there no longer here, once I cancel my order my pantry credits don't reappear? I have the pantry credit, but my $4.99 or the $5.99 (shipping credit),appeared when I did G25PPAOH but now for a real order there gone.