That VNA stuff appears to be more critical to what I was aware of.
The technique of nanoVNA designer edy555 is worth reviewing:
"Remove the crystal filter and connect the resistors to get through characteristics.
Next, disconnect the resistors and take isolation characteristics, and CAL DONE in that state.
In this case, the loss due to resistance and the leakage due to wiring and jigs are cancelled."
Oristo