On the advanced roadmap, why do I have 3 issues without parents even if they have EPIC link?

[Charlène Mao]

Hello, 

I have the advanced roadmap on Jira. 

All my issues have their EPIC links, but On my roadmap, it is written that there are "3 issues without parents".

Is it a bug with Jira? 

Best Regards, 

Charlène