We have a Live Plan created that is tied to a single board as the source.

We are seeing that not all issues under the epics are showing up for import into Live Plans (as well as obviously seeing them in the imported scope). The issue types are custom standard issue types. The Portfolio admin screen shows that all standard issue types are mapped solely to the story level. Some issues under the epic show up (2 out of 20).

If we take that same filter and apply it to a Classic Plan, all the issues under the epics are available for import.

We have followed the checklist mentioned in this answers article:
https://answers.atlassian.com/questions/38390402/issues-not-showing-up-in-portfolio-live-plans

Everything from that list checks out and we are just not sure that this isn't a bug of some sort.