How to check multiple strings in 2 cells and generate another strings based on conditions?

I'm trying to make a "Role Description generator" for my employee based on a Google Sheet in which i have multiple sheets :

1. 1st Sheet : "Positions and Responsabilities"In this sheet I Have all the descriptions of the roles.In the first column I have all the positions associate with each Role. The positions are strings of text separate by a ",".
2. 2nd Sheet : People and PositionsIn this sheet I have all the Employee with each position associated
3. 3rd Sheet : "People Responsabilites"In this Sheet I am trying to generate a list of roles based on a people.I've tried a workaround which seems be working based on queries. But the formula does not work every time (blank position...)

What I am trying to to do :In the Sheet "Positions and Responsabilities" I would like to fill in the last Column "People" with a list of people associated with each position, separated with ","So I can simplify the process of generating the last sheet...

Here is a link of an example : https://docs.google.com/spreadsheets/d/1-jolPlw72FpFdViRm6J2jDiiGDTLMuurmpo7hq06J6Y/edit?usp=sharing

Thank You for your Help !Stephane