Getting error code 500 while adding unsubscribe column in Reports

Hello Team,
I added the unsubscribe option from columns, I got the error code 500. Could you please point out to me what is wrong here?
When I remove the unsubscribe option, it works, but I need this option in my report. Attaching the screenshot for your reference.
Would appreciate urgent help on this as I have been stuck for quite some time.

My purpose was to see the number of unsubscribes in one place with respect to a particular campaign.