CST - Touchstone export not working properly

Hello everyone,
I have a problem regarding the export of a S1P touchstone-file. I modeled and optimized a biquad antenna with a single waveguide port. However, when exporting the S11 parameter as a touchstone-file the output does not look anything like the simulation. The problem still occurs when running CST on another computer. The problem does not occur in other CST models. I have added the images of the data in CST and in another viewer. Does someone know the solution to the problem?