Roofing Detail Parapet Wall and Epdm

I am enclosing 2 pics of the flat roof and parapet wall, The wall has a cap flashing. The previous installers ran the EPDM up the wall but 3" below the cap flashing.

Result. Peeling away with water issues. starting. We are thinking of using 12" wide EPDP slipping it under the flashing and then adhering to the deck. Yes using solvent etc

Question is there a 12" wide one sided stick down detail we can use to accomplish the same thing?

Can you cover the prep and installation for this.

Thanks Joe