I have a VI, which does not make any calls to any other DLLs.
I built it as an exported function in an interop assembly from LabVIEW.
If I then try to call that same built DLL from the same instance of LabVIEW, it loads the function fine and I can wire it up, but it fails to execute, throwing an error that it cannot find NationalInstruments.LabVIEW.Interop.dll. That assembly does exist, but it was installed by LabVIEW to a different location than where it is being linked in the assembly build.