I have to assume that this is a 26.000MHz crystal. The Fp is higher than that. It should be lower so that when you load the crystal that the frequency increases from there. So these numbers do not look good.
I would say that the calibration is at issue here. There is an app note at this link . It shows the pi network for the 50 ohm measurement system.
Other than that, you need to assure that the calibration is done properly at the crystal point with this pi network in the system. The open needs to be about .1 pF. The short needs to be less than 0.1 ohms and the 50 ohm resistive load needs to have less than 10 nH of inductance.
The traces look good. More data points will render better values as well. Zoom in on the 26MHz area as this VNA may not have enough data points with this sweep to give decent numbers. Now that I think about it,that may be all you need. You don't need all that area showing the Fs.
I have hardly turned mine VNA on. I have not looked at crystals as I need to build a pi network fixture. I don't know how small a frequency span you can get.
Jerry N9XR
Jerry Shirar