I used FetishNightFall 11.9 and then updated it with Savie's patch for GU62 and my Mercenary will Resume and Dismiss from the Persona window provided by Savie.
I guess I would suggest anyone having an issue start by repatching with Savie's
Fetish GU62 Patch.
If someone can nail down any specifics I will try to track them down if Savie does not get to them first. In this instance, however, the code is pretty cut and dry and does not appear problematic.