Hi,
I sent my email address through the 'start a conversation' feature of this forum.
I also set up an EVM on my bench with a 450M signal split and fed to both inputs of the ADC. I set the sample rate a 560M since i did not have a filter available for the 580M that you had in your plots. Please see attached. I also set it up with both inputs set to 250M and sample rate 737M since I had those filters out for something else at the time. I don't see what you see, so I think we need to look deeper into what you have set up.
Regards,
Richard P.