Subject line not updating from email in Default Program nested in Nurture Program

I'm not sure why this is happening. Any ideas are appreciated!

I have a Nurture Program with a Default Program nested within it. The default program's smart campaign is used to send three different email assets based on if the record has interest indicated in a custom SFDC field. Screenshot below: 

Each email asset in the default program has a unique subject line (Subject Line A, Subject Line B, and Subject Line C) (and each asset is approved). However, when triggering, each of the three emails uses a new subject line (Subject line D) for all three emails. Interestingly, it is the subject line for the next email in the nurture series (02-Email-Programs) which comes after another nested default program in the stream (01.3-Special Promotions-Texas Fellowship). 

Any ideas why my nested emails are not using the right subject lines when triggered? Happy to provide more screenshots if helpful.