I added vendor name to the notification emails and it works on most but not all of them

[mysticmac]

{% assign line_vendor = line.product.vendor %} 
{{ line_vendor }}

I used the above to add the vendor name to Notification Emails, and it works for all of the Order Notification emails, but not the Shipping Confirmation Notification email.

Code works on these and vendor displays:

Code doesn’t work on these and vendor doesn’t display:

It’s the same code so I can’t figure out why it works on some of the Notifications but not all of them. Any ideas? Thanks