Cannot use Chocobo while Duty Finder is active.

[Conradus]

We cannot use our Chocobos while the Duty Finder is active. If we summon our Chocobos while the Duty Finder is active, it'll cancel the Duty Finder. And we cannot use the Duty Finder while our Chocobos are out. Please fix this.

The problem is, your Chocobo forms a party with you. You can't be in a party when Duty Finder is active because when Duty Finder activates, it's going to want to auto-form a new party for you. As near as I can tell, this is pretty much built into the structure of how chocobo companions, parties and Duty Finder work and interact with each other.