So this is all on me, but i'm following up to my own thread in-case someone ends up
being as boneheaded as me.
In my case I was supplying the value of the iso id dynamically from a config file, what I
did not notice until I did some basic listings side by side, after performing the api
action and after running the gui update, was a clear as day difference in the name of the
iso being referenced. This explains why it would never choose the correct iso (in the gui)
and why the error referenced "Invalid ISO image path". Now i'll be adding
validation that checks available ISOs in the domain, and if the name doesn't match an
available iso it throws an error in the logs.
Live and learn, sigh.