Hi Sarthak,
It seems to be similar, but not the same, as the reported known issue, 55027 - SAS® Visual Analytics might display a "cannot be cast" exception when you attempt to open a ... In the support note, it mentions that a hotfix is planned. I'd suggest to log your issue to SAS Technical Support.
As a workaround, you could make a copy of the exploration and delete the calculated item to see if you can export the exploration as a report. If you can export it as a report with no errors then it was the calculated item definition being the cause. You could then recreate the calculated item in Designer. Of course, any previous reference to the calculated item would be removed and needs to be reassigned in Designer.
Let us know how you go.
Kind Regards,
Michelle
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