First...great tool, I love it.

When I look at a S13 Insertion Loss of a 4 port S-parameter with your online tool I do see a difference when loading this same s-parameter in the LeCroy Wavepulser40i S-parameter viewer.

The result are significant where I get -19.65dB@2.5GHz in the online tool and -15.64db@2.5GHz with the LeCroy tool.

Any idea where the difference is coming from?

The SP4 files that I'm looking at are from USB.ORG:
https://usb.org/document-library/usb-31-embedding-files

USB31_Embedding_Files\Embedding Files\5G_Standard_A\USB3_DEVICE_TEST_SPARAMS.s4p

Also when using this file the EYE diagram calculation hang at 85%.