Sorry, yes. I understood it was a build from Unity3D. I was just trying to understand the failure mode better.
This seems relevant then: https://wiki.samba.org/index.php/Setting_up_a_Share_Using_POSIX_ACLs#Making_Files_Executable
I forget the details of how to modify the system config on the Deck because it's atomic, but I'll poke at it in a bit.